In a change from previous SAV distribution and abundance reports in this series, SAV distribution data in this report are presented and discussed based on the segmentation scheme adopted by the Chesapeake Bay Program (U.S. EPA, 1983) and described briefly in the Methods section of this report (Tables 3 and 4; Figure 9). A new zonation scheme (Upper, Middle, and Lower zones) for Chesapeake Bay, which accommodates the Chesapeake Bay Program segmentation boundaries (Figure 9), was adapted from that used in previous SAV distribution reports (i.e., Orth et al., 1994) and established by Orth and Moore (1982), then modified by Orth et al. (1989). SAV distribution data for the years 1991-1994 are presented using the Chesapeake Bay Program segmentation scheme in order to consistently follow up the recently published EPA report on trends in SAV (Orth et al., 1995), which covers the years 1971-1991 using the same scheme.
The 1991-1993 data were edgematched using ARC/INFO GIS software, as were the 1994 data, in order to bring separately digitized USGS 7.5 minute topographic quadrangle SAV coverages into one unified coverage for the entire Chesapeake Bay (see Methods). Therefore, 1991-1993 SAV distribution data presented in this report reflect edgematching adjustments, and differ from previously published data for these years derived from separate coverages which were not edgematched (i.e., Orth et al., 1992, 1993, and 1994).
SAV distribution data for 1991-1994 are presented in hectares, by quadrangle (Table 5), by zone (Figure 2), by Chesapeake Bay Program segment and zone (Figures 3, 4, and 5; Table 6), and by quadrangles within segments (Table 7). Distribution data for 1994 by density class are presented in hectares for each segment (Table 8). Distribution data for 1991-1994 by density class are presented in hectares per segment in Appendix E, and in hectares per zone in Table 9. Quadrangle maps annotated with all 1994 SAV beds, and with 1994 ground-truth data, are presented in Appendix B, whereas all ground-truth data for 1994 are also tabulated in Appendix D. The calculated areas for individual SAV beds for each quadrangle are given in square meters in Appendix C.
The 1994 distribution data are summarized and compared with results from 1993 distribution and abundance data. The 1991-1994 SAV distribution data are discussed relative to the Upper, Middle, and Lower Bay zones. The 45 segments of the Chesapeake Bay, and Chincoteague Bay, are then discussed either individually or as combined groups, and the 1994 data are compared with results from 1991-1993 SAV distribution and abundance data. The 1994 distribution of SAV is plotted for each Chesapeake Bay segment, and for Chincoteague Bay. SAV beds are plotted in red; and bold, black lines represent segment boundaries. USGS 7.5 minute quadrangles are represented on these segment plots by a grid of numbered rectangles (refer to Table 2 for quadrangle names listed by VIMS map number). Specific names of rivers, creeks, or points of land, which are not found on the segment plots, are on the quadrangle maps for that segment (Appendix B). Ground-truth data for 1994 are discussed for each Chesapeake Bay Program segment and for Chincoteague Bay.
In 1994, the Chesapeake Bay had 26,484 hectares of SAV, compared with 29,587 hectares in 1993, a decrease of 10%, with 3,854 hectares (15%), 13,373 hectares (50%), and 9,257 hectares (35%) occurring in the Upper, Middle, and Lower Bay zones, respectively (Figures 1 and 2; Tables 5 and 6). SAV increased in the Upper zone by 44%, and decreased in the Middle and Lower zones 21% and 8%, respectively, from totals in 1993 (Figure 2; Table 6). SAV increased in abundance from 1993 levels in all segments in the Upper Bay zone except WT1 (Bush River) and WT4 (Back River), which remained unvegetated (Table 6). Increases in 1994 for some segments (e.g., TF1 and CB8) of the Middle and Lower zones did not offset larger decreases in 1994 in other segments (e.g., CB5, TF2, EE3, CB7, and LE3) of these zones (Table 6).
In 1994, SAV in the Bay increased, compared with 1993 levels, in twenty segments (Upper zone: CB1, CB2, CB3, WT2, WT3, WT5, WT6, ET1, ET2, ET3, ET4; Middle zone: WT7, WT8, TF1, RET1, LE2, EE1; and Lower zone: CB8, LE4, LE5), decreased in fourteen (Middle zone: CB4, CB5, LE1, TF2, RET2, ET5, ET8, ET9, EE2, EE3; and Lower zone: CB6, CB7, LE3, WE4), and remained unvegetated in eleven (Upper zone: WT1, WT4; Middle zone: ET6, ET7, ET10; and Lower zone: TF3, RET3, TF4, RET4, TF5, RET5) (Table 6). SAV was not detected in 1994 in fourteen segments (Upper zone: WT1, WT4; Middle zone: CB4, LE1, ET5, ET6, ET7, ET10; and Lower zone: TF3, RET3, TF4, RET4, TF5, RET5) (Figures 3, 4, and 5) as compared to sixteen segments in 1993 (Table 6). [The mainstem upper and middle Rappahannock River, TF3 and RET3, upper and middle York River, TF4 and RET4, and upper and middle James River, TF5 and RET5, have been totally devoid of submerged vegetation for years and are not currently photographed (Methods; Figure 6)]. Five segments (Upper zone: WT5, ET1; and Middle zone: WT7, WT8, RET1), which were unvegetated in 1993, had some SAV detected by photography in 1994 (Table 6). Three segments (CB4, LE1, and ET5), all in the Middle zone, which were vegetated in 1993, albeit with relatively small amounts, had no SAV detected in 1994 (Table 6).
In the Bay in 1994, 36% of SAV was categorized as dense (density class 4, or 70-100% coverage), up slightly from the 1993 amount (32%) (Table 9). The percentage of SAV categorized as moderate (density class 3, or 40-70% coverage) in 1994 (19%) also increased slightly from that in 1993 (18%) (Table 9). The percentage of SAV categorized as sparse (density class 2, or 10-40% coverage) (28%) decreased in 1994 compared with that in 1993 (34%), whereas that categorized as very sparse (density class 1, or 1-10% coverage) (17%) increased slightly in 1994 from that in 1993 (15%) (Table 9). SAV in the very sparse and sparse classes combined (the 0-40% coverage range) constituted 45% of all SAV in 1994, a decrease from 49% in 1993 (Table 9). Conversely, SAV in the moderate and dense classes combined (the 40-100% coverage range) constituted 55% of all SAV in 1994, an increase from 51% in 1993 (Table 9).
The total SAV in Chesapeake Bay increased each year from 1991 to 1993, then decreased in 1994 (Table 6). However, the 1994 level of 26,484 hectares was still 859 hectares greater than the 1991 level of 25,625 hectares (Table 6). SAV in the Chesapeake Bay increased in all zones each year from 1991 to 1993, although not all segments within zones exhibited a steadily increasing trend (Figure 2; Tables 6 and 7). However, yearly gains in some segments offset losses in others, generally, resulting in increasing zone totals from 1991 through 1993 (Table 6). Then in 1994, the Upper Bay zone total continued to increase (44%) from 2,672 hectares the previous year to 3,854 hectares, the highest level in four years and an increase of 1,696 hectares over 1991 (Figure 2; Table 6). However, in 1994 the Middle and Lower zone totals both decreased from 1993 levels, 16,825 to 13,373 hectares (21%) and 10,091 to 9,257 hectares (8%), respectively (Figure 2; Table 6). The 1994 Middle zone total of 13,373 hectares was the lowest level in four years (a decrease of 921 hectares from 1991; a decrease of 3,452 hectares from the same period's highest level in 1993) (Figure 2; Table 6). The 1994 Lower zone total of 9,257 hectares, although an 834 hectare decrease from its high for this four-year period in 1993, was still 84 hectares greater than the 1991 level (Figure 2; Table 6).
In the Bay in 1994, compared with 1991, SAV increased in twenty-three segments (Upper zone: CB1, CB2, CB3, WT2, WT3, WT5, WT6, ET1, ET3, ET4; Middle zone: WT7, WT8, TF1, RET1, LE2, EE1, EE2; and Lower zone: CB6, CB7, CB8, LE4, WE4, LE5), decreased in nine segments (Upper zone: ET2; Middle zone: CB4, CB5, TF2, RET2, ET8, ET9, EE3; and Lower zone: LE3), and was similarly unvegetated in thirteen segments (Upper zone: WT1, WT4; Middle zone: LE1, ET5, ET6, ET7, ET10; and Lower zone: TF3, RET3, TF4, RET4, TF5, RET5) (Tables 6 and 7).
In Chesapeake Bay, taken as a whole over the period 1991 to 1994, the percentage of SAV categorized as dense decreased 28% (Table 9). In 1991, 50% of SAV in the Bay was in density class 4, but in 1994 this percentage was only 36% (Table 9). The percentage of SAV in this class declined each year from 1991 until 1994, when it increased to 36%, its second highest level in the four-year period (Table 9). That is a 13% increase from the four-year low in 1993 of 32% (Table 9). Conversely, in the same four-year period, the percentage of SAV categorized as sparse increased 47% (Table 9). In 1991, 19% of SAV in the Bay was in density class 2, but by 1994 this percentage was 28% (Table 9). The percentage of SAV in this class increased each year from 1991 until 1994, when it decreased to 28%, its third highest level in four years (Table 9). That is an 18% decrease from the four-year high of 34% in 1993 (Table 9).
The percentages of SAV in density classes 1 and 3 also increased from 1991 to 1994, although these increases were not as great as for density class 2 (Table 9). The percentage of SAV in density class 1 increased each year from 1991 to 1994 (Table 9). In 1991, 12% of Bay SAV was categorized as very sparse, but by 1994 this figure was 17% (Table 9). The percentage of SAV in density class 3 in 1991 was 18%, in 1992 it was 26%, in 1993 it was 18%, and in 1994 it was 19% (Table 9). In the Bay from 1991 to 1994, there was a 45% increase in the percentage of SAV in the sparse and very sparse classes combined (the 0-40% coverage range) (Table 9). The percentage of SAV in combined classes 1 and 2 increased from 31% in 1991, to 49% in 1993, but in 1994 there was a decrease to 45% of the SAV (Table 9). Conversely, there was a 20% decrease in the percentage of SAV in the moderate to dense classes combined (the 40-100% coverage range) from 1991 to 1994 (Table 9). The percentage of SAV in combined classes 3 and 4 decreased from 69% in 1991 to 51% in 1993, then increased in 1994 to 55% (Table 9).
The total SAV coverage in the Upper Bay zone increased 44% from 1993 (2,672 hectares) to 1994 (3,854 hectares) (Table 6). The total SAV level in the Upper Bay zone increased each year from 1991 to 1994, for an overall 79% (1,696 hectares) increase (Table 6).
SAV in the Upper Bay zone, taken as a percentage of the SAV in the whole Chesapeake Bay, increased each year since 1991 (Table 6). It increased less than a percentage point each year from 1991 to 1993, going from 8% to 9%; then in 1994 it jumped to 15% of SAV in the Bay (Table 6).
Of the thirteen segments comprising this zone, there were increases in SAV abundance over 1993 levels in eleven segments, of which ten had increases in SAV over 1991 levels, also (Table 6). Of the latter ten segments, eight segments (CB1, CB2, CB3, WT5, WT6, ET1, ET3, and ET4) were at their highest levels since 1991, and two of those segments, the Patapsco River (WT5) and the Northeast River (ET1), had SAV for the first time in this four-year period (Tables 6 and 7). The remaining two segments, the Gunpowder River (WT2) and the Middle River (WT3) reached their highest levels for this four-year period in 1992, then decreased in 1993, and rebounded in 1994 to their second highest levels since 1991 (Tables 6 and 7).
Only one segment (ET2) had less SAV (180 hectares) in 1994 than in 1991 (269 hectares), although this was an increase from its lowest level of 95 hectares in 1993 (Tables 6 and 7). SAV in 1994 in segment ET2, the Elk and Bohemia Rivers, increased 89% over 1993 (95 to 180 hectares), but this was still less than the four-year high for the period in 1991 of 269 hectares (Tables 6 and 7). Two segments, the Bush River (WT1) and the Back River (WT4) were unvegetated in 1994 and 1991. However, WT1 had some vegetation (2.32 hectares) mapped in 1992; whereas, only WT4 had no vegetation mapped in any year for the entire 1991 to 1994 period (Tables 6 and 7).
The amount of SAV in the Middle Bay zone decreased 21%, or 3,452 hectares, from 1993, to a total of 13,373 hectares in 1994, which was the lowest level in four years (Table 6). The SAV in the Middle Bay zone increased each year from 1991 to 1993, for an overall increase of 18% (2,531 hectares), but the 1994 level was 921 hectares or 6% less than the 1991 level (Table 6).
SAV in the Middle Bay zone, taken as a percentage of the total SAV in the Chesapeake Bay, declined in 1994 from 1991-1993 levels (Table 6). In 1991 it was 56% of SAV in the Bay; in 1992 it was 58%; in 1993, 57%; and in 1994 it dropped over 6 percentage points to 50% (Table 6). [This corresponded to concomitant increases in the other two zones (Table 6).]
Of the nineteen segments comprising this zone, there were increases in 1994 SAV abundance over 1993 levels in six segments (WT7, WT8, TF1, RET1, LE2, and EE1), which were also at their highest levels for the four-year period as well (Tables 6 and 7). In addition, three of the latter segments, the Severn River (WT7), the South, Rhode, and West rivers (WT8), and the Middle Patuxent River (RET1), had SAV for the first time in the four-year period (Tables 6 and 7). The Upper Patuxent River segment (TF1) was unvegetated in 1991 and 1992 as well, but had 8.78 hectares in 1993 (Tables 6 and 7).
In the Middle Bay zone in 1994, there were decreases from 1993 levels in ten segments (CB4, CB5, LE1, TF2, RET2, ET5, ET8, ET9, EE2, and EE3) (Tables 6 and 7). Six of the latter segments (CB4, LE1, ET8, ET9, EE2, and EE3) in 1993 were at their highest levels since 1991 (Tables 6 and 7). Except segment EE2, the Lower Choptank River, which was still 1,402 hectares higher in 1994 than in 1991, nine of the segments which decreased from 1993 levels reached their lowest levels for this four-year period in 1994 (Tables 6 and 7). This included, among others, the Upper and Middle Potomac River segments (TF2 and RET2) and the two segments (CB5 and EE3) encompassing Tangier, Smith, and Bloodsworth islands, which historically had some of the largest SAV beds in the Bay and, proportionately, the greatest amount of SAV in the Bay (Tables 6 and 7).
In the Middle Bay zone in 1994, there were six unvegetated segments (CB4, LE1, ET5, ET6, ET7, and ET10), the latter three of which were unvegetated each year since 1991 (Tables 6 and 7). The Lower Patuxent River segment (LE1) and the Choptank River (ET5) dropped back to their 1991 unvegetated condition after both had small amounts of SAV recorded in the intervening period (Tables 6 and 7). The Middle Central Chesapeake Bay segment, CB4, was vegetated in 1991, as well as in 1992 and 1993 (Tables 6 and 7).
The total SAV level in the Lower Bay zone decreased 8% or 834 hectares from 1993 to 1994 (Table 6). The total SAV level in the Lower Bay zone increased each year, from 1991 to 1993, for an overall increase of 918 hectares or 10%. SAV then decreased in 1994, but this level (9,257 hectares) was still 85 hectares greater than the 1991 level (9,173 hectares) (Table 6).
SAV in the Lower Bay Zone, as a percentage of the SAV in the entire Chesapeake Bay, declined from the 1991 level of 36%, to 35% in 1994 (Table 6). It dropped to 33% in 1992, then increased in 1993, to 34%, and again in 1994 (Table 6).
Of the thirteen segments comprising this zone, there were increases in 1994 in SAV abundance over 1993 levels in three segments (CB8, LE4, and LE5), which also were at their highest levels in the four years since 1991 (Tables 6 and 7). In 1994, four segments (CB6, CB7, LE3, and WE4) in the Lower Bay zone, which were consistently increasing each year since 1991, decreased from 1993 levels, which were the highest for the four-year period (Tables 6 and 7). In this zone in 1994, only one segment, LE3, the Lower Rappahannock River, decreased to a level (197 hectares) below that of 1991 (315 hectares) (Table 6).
In the Lower Bay zone, six segments (TF3, RET3, TF4, RET4, TF5, and RET5) which comprise the upper and middle segments of three major bay tributaries, the Rappahannock, the York, and the James, remained unvegetated from 1991 to 1994 (Tables 6 and 7). These six segments have been unvegetated for years and are no longer photographed (see Methods).
In 1994, SAV levels for six segments (CB6, CB7, CB8, LE4, WE4, and LE5) were higher than their 1991 levels, although three of these segments (CB6, CB7, and WE4) actually decreased from their 1993 levels, which were the highest for the four-year period (Tables 6 and 7).
The amount of SAV in this segment increased 58% since 1991, to 2,649.85 hectares in 1994 (Tables 6 and 7). The biggest increase (50%) occurred between 1993 and 1994 (Tables 6 and 7).
Since 1991, the Northern Chesapeake Bay segment (CB1) consistently had the largest percentage of SAV in the Upper Bay zone (Tables 6 and 7). In 1994, 69% (2,649.85 hectares) of the SAV in this zone was in segment CB1 (Table 6). This is an increase from the 1993 level, when 66% of SAV in the Upper Bay zone (or 1770.18 hectares) was in CB1; however, this is a decrease from 71% in 1992 and from 78% in 1991 (Tables 6 and 7). These decreases reflect concomitant increases in SAV abundance in other segments of this zone, primarily CB2, CB3, WT3, WT6, ET1, ET3, and ET4 (Table 6).
In the Northern Chesapeake Bay segment in 1994 , 87% of all SAV beds were classified as very sparse (0-10% coverage); 5% were sparse (10-40% coverage); 2% were moderate (40-70% coverage); whereas 6% of beds were classified as dense (70-100% coverage) (Table 8; Figure 3, Appendix E). In this segment in 1993, 86% was very sparse, 4% was sparse, 3% was moderate, 8% was dense (Appendix E). Although there was a slight decline in the percentage of SAV in density class 1 from the 1991 level (89%), this was essentially the same pattern of density distributions recorded since 1991: class 1 constituting more than 80% of the SAV in this segment and lesser amounts distributed in the other three density classes (Appendix E). The percentage of SAV in density class 2, and in density class 3, although still small in 1994, has increased slightly from 1991 (Appendix E). The percentage of density class 4, also small in 1994, has decreased slightly from that in 1991 (Appendix E).
SAV beds were located in six main areas: 1) sparse to dense fringing beds in the Susquehanna River from Robert Island to the river mouth at Havre de Grace on the west side; to Stump Point at the mouth of Mill Creek on the east side; and in Mill Creek, Furnace Bay, Baker Cove, and at High Point; 2) a large area of very sparse SAV located in the broad shoal area at the Susquehanna River mouth; 3) very sparse to dense beds fringing the shore from Concord Point south to Swan Creek; 4) a large area of predominately very sparse beds located south of Havre de Grace to east of Battery Island; 5) small, fringing beds of very sparse to moderate density in the Spesutie Narrows; and 6) a new 38.6 hectare SAV area east of Spesutie Island (Figure 10; Appendix B, Maps 2, 3, and 9). The SAV beds listed under number 4, above (the predominately very sparse areas south of Havre de Grace to east of Battery Island), constituting approximately 680 hectares, were mostly new for 1994 and represent 26% of the SAV in CB1 in 1994, as well as 77% of the increase in total abundance over 1993 (Tables 6 and 7; Figure 10; Appendix B, Maps 3 and 9; Appendix C, Map 3, Bed BA1, and Map 9, Beds ZA1 and BA1).
A total of eight species of SAV (H. verticillata, M. spicatum, C. demersum, Heteranthera dubia, Vallisneria americana, Najas minor, Najas gracillima, E. canadensis), plus an unknown species, were reported for 1994 on Maps 2, 3, and 9 (Appendices B and D), either by Stan Kollar of Harford Community College or the Citizens' Survey. Hydrilla was reported extending from Robert Island in the Susquehanna River, to the Spesutie Narrows, and to Furnace Bay and the Susquehanna Flats (Appendices B and D and D, Maps 2, 3, and 9) .
These three segments together contained 7% of the SAV in this zone in 1994, approximately half of the 1991 figure (14%) (Tables 6 and 7). Since 1991, segments ET1, ET2 and ET3 have had the majority of their SAV classified as very sparse and sparse (Appendix E). Principal locations of beds were in the Elk River and the lower Sassafras River (Figure 11). Very little SAV was mapped in the Bohemia River. Much of the increase was in the Elk River (Figure 11).
In 1994, SAV mapped was mapped in the Northeast River segment (ET1) for the first time since 1991 (Tables 6 and 7; Figure 11; Appendix B, Map 4). There were 7.96 hectares, of which 5.97 hectares (75%) were classified as very sparse and 1.99 hectares (25%) were classified as moderate (Tables 6, 7 and 8; Appendix E). Only one ground-truth site was surveyed in ET1 for 1994. M. spicatum was reported there by Stan Kollar of Harford Community College (Appendices B and D, Map 4).
The Elk and Bohemia Rivers segment (ET2) had 179.86 hectares in 1994 (Tables 6 and 7; Figure 11; Appendix B, Maps 4 and 10), an increase of 90% from the 1993 level (94.76 hectares) (Tables 6 and 7). However, this was still less than the 1991 level of 268.96 hectares (Tables 6 and 7). Segment ET2 had 70% of SAV in 1994 classified as very sparse, 25% as sparse, 5% as moderate, and none classified as dense (Table 8; Appendix E).
Several sites on both shores in the Elk River were surveyed by Stan Kollar, by the EPA, and by the Citizens' survey in 1994 which all reported M. spicatum and V. americana. In addition, Stan Kollar also reported P. pectinatus and Potamogeton crispus on the north shore, and M. spicatum from Town Point at the mouth of the Bohemia River on the south shore in 1994 (Appendices B and D, Maps 4 and 10).
In 1994, the Sassafras River segment (ET3) had a four-year high of 76.24 hectares, only a slight increase over the 1993 level, but a 153% increase over the 1991 level (Tables 6 and 7; Figure 11, Appendix B, Maps 9, 10, 16, and 17). Segment ET3 had 79% of the SAV classified as very sparse, 6% as sparse, 0% as moderate, and 15% classified as dense (Table 8; Appendix E).
In 1994 Stan Kollar reported M. spicatum from the north shore of the Sassafras River, and M. spicatum and V. americana from the south shore. The Citizens surveyed one site in ET3 and reported an unidentified species of SAV from McGill Creek, off of Back Creek (Appendices B and D and D, Maps 9, 10, 16, and 17).
The Upper Chesapeake Bay segment (CB2) contained 2% or 65.11 hectares of the SAV in this zone in 1994, of which 54% was classified as sparse and 36% is classified as dense (Tables 6, 7 and 8; Appendix E). This is an increase in both total abundance and in the percentage classified as dense over levels in 1991, 1992, and 1993 (Tables 6, 7 and 8; Appendix E). Specifically, in 1993 there were 34.31 hectares mapped with only 5% classified as dense; in 1992 there was somewhat more SAV (49.57 hectares) but with none classified as dense; and in 1991 the total abundance of CB2 was a four-year low of 31.90 hectares, again with none classified as dense (Tables 6 and 7; Appendix E). SAV was mapped from the lower Spesutie Narrows and Little Romney, Romney, and Delph creeks on the western shore of the bay; and Pond, Still Pond, and Fairlee creeks, on the eastern shore of the bay (Figure 12; Appendix B, Maps 8, 9, 10, and 15).
In 1994, only M. spicatum was reported from groundtruthing by Stan Kollar, at one site near Bear Point and the Spesutie Narrows (Appendices B and D and D, Map 9). The Citizens' survey reported M. spicatum and P. crispus from Still Pond Creek (Appendices B and D and D, Map 15).
The Upper Central Chesapeake Bay segment (CB3) contained 9% or 332.11 hectares of the SAV in this zone in 1994, 79% of which was classified as dense (Tables 6, 7 and 8; Appendix E). The total abundance in 1994 was similar to that in 1993 (324.15 hectares), when, however, only 56% of SAV was classified as dense (Tables 6 and 7; Appendix E). The 1994 levels contrasted with 1991 when CB3 had only 1% or 22.87 hectares of SAV in the zone, 76% of which was sparse and only 15% was dense ((Tables 6 and 7; Appendix E). SAV was mapped only from the eastern shore of CB3: from Swan Creek, The Haven, and Rock Hall Harbor, all east of Swan Point; Huntingfield Creek on the northern end of Eastern Neck; and the western shore of Eastern Neck, south to Calfpasture Cove on Eastern Neck Island (Figure 12; Appendix B, Maps 20, 21, and 26).
In 1994, VIMS and Citizens' surveys reported R. maritima, P. perfoliatus, M. spicatum, and Z. palustris in this segment (Appendices B and D, Maps 13, 19, and 26). From the western shore the Citizens' survey reported M. spicatum from Brown's Creek, and M. spicatum and Z. palustris from Shallow Creek (Appendices B and D, Maps 13 and 19). From the eastern shore of CB3, VIMS reported R. maritima, P. perfoliatus, and M. spicatum from the large SAV bed adjacent to the west side of Eastern Neck (Appendices B and D, Map 26)
No SAV was reported in the Bush (WT1) or Back (WT4) river segments in 1994, the same as in 1991 and in 1993 (Tables 6 and 7). Only the Bush River segment had some SAV (2.32 hectares, density class 3) in 1992 (Tables 6 and 7; Appendix E). Ground-survey data for 1994 for WT1 from the Citizens' survey cited C. demersum, M. spicatum, and V. americana in Otter Point Creek (Appendices B and D, Map 7).
Although no SAV was reported in the Patapsco River segment (WT5) during 1991-1993, in 1994 there was less than a hectare (0.37 hectares; density class 2) of SAV mapped from aerial photography (Tables 6, 7 and 8; Appendix E). The SAV in segment WT5 was located in the mouth of Rock Creek, a tributary entering at the mouth of the Patapsco River (Figure 13; Appendices B and C, Map 18). There was no ground-truth data for WT5 in 1994.
The Gunpowder and Middle river segments (WT2 and WT3, respectively) were vegetated each year, 1991-1994 (Tables 6 and 7). The SAV increased in 1994 in both segments over 1993 levels, however; 1994 levels were still less than the four-year highs in 1992 (Tables 6 and 7). Specifically, the Gunpowder River segment had 89.25 hectares in 1994, a 92% increase over the amount in 1993 (46.60 hectares), although this was still 36.83 hectares less than the 1992 level of 126.08 hectares (Tables 6 and 7). However, 44% of the SAV in 1994 was classified as Class 4 (dense), a significant increase in density over the previous three years (1991 and 1993 had 0% Class 4 density; 1992 had 11%) (Table 8; Appendix E). Similarly, the Middle River segment increased from 6.67 hectares in 1993 to 25.02 hectares in 1994, although this was still 20.70 hectares less than the 1992 level of 45.72 hectares (Tables 6 and 7). There was no SAV classified as dense in the years 1991-1994, however, 53% was classified as moderate in 1994, a significant increase over 1993 when 0% was classified as moderate (Table 8; Appendix E).
In 1994, in segment WT2, SAV was located in the Gunpowder River at the mouth of the Gunpowder Falls, along the Gunpowder Neck shore, and in Dundee and Saltpeter creeks, two tributaries near the mouth (Figure 13; Appendix B, Maps 7 and 14). In 1993 SAV was noticeably reduced in Saltpeter Creek from that in 1992 (Orth et al., 1994; 1993), but in 1994 (Figure 13) there was some recovery of those beds. In 1994, Stan Kollar reported M. spicatum and V. americana at the mouth of Gunpowder Falls (Appendices B and D, Map 7). Also, Stan Kollar and Essex Community College reported M. spicatum, V. americana, E. canadensis, C. demersum, and Chara from Dundee Creek, and reported M. spicatum, E. canadensis, and C. demersum from Saltpeter Creek (Appendices B and D, Map 14).
In 1994, in segment WT3, SAV was located in the Middle River, in Seneca Creek, and in Hawthorn Cove at the mouth of Seneca Creek (Figure 13; Appendix B, Maps 13 and 14). In 1993, SAV in Seneca Creek, as with Saltpeter Creek in segment WT2 with which it is connected, was noticeably reduced from that in 1992 (Orth et al., 1993; 1992). In fact it was absent from Seneca Creek in 1993 except for one fringing bed in Hawthorn Cove (Orth et al., 1994). However, as with Saltpeter Creek, in 1994 there was some recovery of SAV beds (Figure 13). In 1994, M. spicatum and R. maritima were reported from the Middle River by Citizens (Appendices B and D, Map 13). Also, Stan Kollar reported M. spicatum, E. canadensis, V. americana, C. demersum, Najas guadalupensis, and P. perfoliatus from the Seneca Creek and Hawthorn Cove area (Appendices B and D, Map 14).
In the Chester River Segment (ET4), SAV abundance (409.50 hectares) was up 103.3 hectares from 1993 (Tables 6 and 7). There were only 33.81 hectares of SAV in the Chester River segment in 1991 (Tables 6 and 7). The Chester River segment contained 11% of SAV in this zone, up from 2% in 1991 (Table 6). In this segment in 1994, 49% of the total coverage of SAV was dense (class 4), 28% was moderate (class 3), 18% was sparse (class 2), and 5% was very sparse (class 1) (Table 8; Appendix E). There was a notable increase in SAV classified as dense since 1991, when only 7% was dense (Appendix E). Most of the SAV was located adjacent to Eastern Neck and Eastern Neck Island, especially near Eastern Neck Narrows, and in Church, Grays Inn, Langford, and Queenstown creeks, tributaries entering the Chester River (Figure 14; Appendix B, Maps 21, 26, 32, and 33). In 1994, the Citizens cited M. spicatum, P. perfoliatus, and Z. palustris on the south shore of the Chester River (Appendices B and D, Map 33).
There were 18.54 hectares of SAV reported in WT6 in 1994, 47% of which was classified as moderate and 10% was classified as dense (Tables 6, 7 and 8; Appendix E). This is an increase in both distribution and abundance compared to 1993 when 13.21 hectares were reported, 5% of which was classified as moderate and 0% was classified as dense (Tables 6 and 7; Appendix E). In 1993, SAV was mapped in the Magothy River (WT6) for the first time since last reported in 1987 (Orth et al., 1994).
SAV was located primarily near Ulmsteads Point, on the south shore; and on the north shore: adjacent to Dobbins Island at the mouth of Sillery Bay; along the east shore of Sillery Bay; in Cornfield Creek; and in the Magothy Narrows, around parts of Gibson Island (Figure 15; Appendix B, Maps 23 and 24).
Five species were reported by the Citizens' survey in 1994: Potomageton perfoliatus, Z. palustris, R. maritima, V. americana, and P. pectinatus (Appendices B and D, Maps 23 and 24). Zannichellia palustris and P. perfoliatus were reported from the headwaters to the Magothy Narrows, whereas P. pectinatus and R. maritima were reported from approximately the middle river portion to the Narrows (Appendices B and D, Maps 23 and 24). Vallisneria americana was reported only from two sites, one in the Narrows and one in Cornfield Creek which flows into the Narrows (Appendices B and D, Map 24).
In the Severn River segment (WT7) in 1994, there were 31.32 hectares of SAV reported, compared with 0.0 hectares reported during 1991- 1993 (Tables 6 and 7). In this segment in 1994, no SAV was classified as dense, but 53% was classified as moderate, 34% was sparse, and 12% was very sparse (Table 8; Appendix E). The SAV was located primarily from Round Bay downstream to Asquith Creek (Figure 15; Appendix B, Map 23). In 1994, Citizens and VIMS provided species information for WT7: R. maritima, P. perfoliatus, Z. palustris, and an unknown species were reported (Appendices B and D). There was no ground-truth data from the headwaters portion. Ruppia maritima and P. perfoliatus were generally found in the, middle portion, whereas Z. palustris was found in the lower third portion and near the mouth (Appendices B and D, Maps 23 and 31).
In the South, Rhode, and West rivers segment (WT8) in 1994, there were 6.36 hectares of SAV reported, compared to 0.0 hectares reported 1991- 1993 (Tables 6 and 7). The majority (86%) was classified as sparse and the rest (14%) was moderate (Table 8; Appendix E). The SAV was located primarily in the South River at the mouths of Aberdeen and Brewer creeks, and at the mouth of the West River in Parish Creek (Figure 15; Appendix B, Maps 30 and 35). No SAV was mapped from the Rhode River in 1994, as in 1991-1993 (Figure 15). In 1994, the Citizens' survey found Z. palustris and R. maritima at numerous locations in the South and Rhode rivers and an unknown species was also cited (Appendices B and D, Maps 30, 31, and 35).
In the Eastern Bay segment (EE1), there were 976.14 hectares of SAV reported in 1994, compared with 733.71 hectares of SAV reported in 1993 (Tables 6 and 7). SAV increased each year from 1991-1994 in this area (Tables 6 and 7). Only 67.93 hectares were reported in 1991 (Tables 6 and 7). Most of the increases occurred in Warehouse Creek of Eastern Bay, in Marshy and Kirwan creeks of Prospect Bay, and in the Miles River (Figure 16; Appendix B, Maps 32, 33, 36, and 37). In this segment in 1994, 4% of SAV was dense, 36% was moderate, 49% was sparse, and 11% was very sparse (Table 8; Appendix E). Contrast this with 1993, when 2% was dense, 17% was moderate, 12% was sparse, and 69% was very sparse (Table 8; Appendix E).
Most of the SAV in segment EE1 was located in the lower Miles River; Wye River; Cox Creek; Eastern, Prospect, and Crab Alley bays; Parson Island; Piney Neck; and between Harbor Cove and Tilghman Point of Eastern Bay (Figure 16). In 1994, VIMS, the EPA, and the Citizens provided ground-truth data for EE1 (Appendices B and D, Maps 32, 33, 36, and 37). Prospect Bay had two sites with Z. palustris; Parson Island and Turkey Point each had one site with both R. maritima and Z. palustris; Tilghman Creek, the Miles River, and Kent Island had several sites with Z. marina, R. maritima, and Z. palustris (Appendices B and D, Maps 32, 33, 36, and 37).
In the Middle Central Chesapeake Bay segment (CB4), there was no SAV mapped in 1994 compared with 4.88 hectares of SAV reported in 1993, which was the high for the 1991-1994 period (Tables 6 and 7; Figure 17). The only ground-truth data for 1994 from CB4 was Zannichellia palustris reported from two creeks flowing into CB4 in the area on the western shore between the mouths of the Severn and South rivers (Appendices B and D, Map 31).
In the Choptank River segment (ET5), there was no SAV mapped in 1994, as in 1991, compared with 4.02 hectares of very sparse SAV reported in 1993 and 5.66 hectares sparse SAV in 1992 (Tables 6 and 7; Figure 18; Appendix E). There was no groundtruth-data for this segment in 1994.
There was a decrease in the amount of SAV in the Lower Choptank River segment (EE2) from 1993 to 1994 (Tables 6 and 7). There were 1,513.61 hectares of SAV mapped in 1994 ((Tables 5 and 7; Appendices B and C, Maps 36, 37, 43, 44, 45, 51, 52, and 62) compared with 1,888.37 hectares of SAV reported in 1993 (Tables 6 and 7). However, the 1994 level was still 1,401.95 hectares more than the 1991 total of 111.66 hectares and 442.30 hectares greater than the 1992 total of 1,071.31 hectares (Tables 6 and 7). Also, from 1991 to 1993, there was very little SAV classified as dense in segment EE2 (0% in 1991; 1% in 1992; and 4% in 1993) (Appendix E). However, in 1994, 42% of the total coverage of SAV was dense; 31% was moderate; 26% was sparse; and 1% was very sparse (Table 8; Figures 2 and 4). Although there was a decline of 375 hectares from 1993, many areas off the Choptank River, from Tilghman Island to the Tred Avon River, showed increases in SAV and also in density class: Harris, Broad, Leadenham, Grace, San Domingo, Cummings, Waterhole, Edge, and Solitude creeks; and Briary Cove. SAV was detected by photography in Trippe Creek for the first time since 1985 (Map 45). There was also an increase in fringing beds in Slaughter Creek and Slaughter Creek Broads (Map 62). The decrease in SAV was noted in Trippe and Brannock bays; Irish Creek; and near Todds Point (Maps 44 and 51). SAV was completely absent in 1994 in Brooks Creek; Hooper Neck; James Island; Hudson and Back creeks; and Casson Point, making the Little Choptank River devoid of SAV for 1994 (Figure 18).
In 1994, R. maritima and Z. palustris were reported from EE2 by VIMS and Citizens' surveys (Appendices B and D, Maps 36, 37, 43, 44, 51, and 52). Both these species were reported from Tilghman Island and the creeks in the northern portion of the segment, whereas only R. maritima was reported from Trippe Bay, and only Z. palustris was reported from the Little Choptank River in the southern portion.
In the Patuxent River (LE1, RET1, TF1), there was an increase of SAV reported in 1994, primarily in the Upper Patuxent River segment (TF1) (Tables 6 and 7).
In the Upper Patuxent River, there were 75.19 hectares of SAV reported in 1994 compared with 8.78 hectares reported in 1993 (Tables 6 and 7). No SAV was mapped in either 1991 or 1992 (Tables 6 and 7). In this segment in 1994, 82% of SAV was classified as dense and the remainder was moderate, contrasted with 1993, when 100% was sparse (Appendix E). The SAV beds were located below Waysons Corner (Route 4 Bridge) to north of Lower Marlboro (Figure 19; Appendix B, Maps 41 and 159). The Bristol quadrangle (Map 159) had SAV by photography for the first time since 1985 (Appendix B; Orth et al., 1986, 1987, 1989, 1991). In 1994, ground truth from the MD-DNR (Naylor and Kazyak, 1995), the Patuxent River Park, and the Citizens' surveys reported C. demersum, E. canadensis, H. verticillata, N. guadalupensis, N. gracillima, N. minor, P. crispus, Potamogeton pusillus, Z. palustris, V. americana, and an unidentified species, primarily in the upper half of TF1 (Appendices B and D, Maps 41, 49, 159).
In the Middle Patuxent River segment (RET1), there were 1.52 hectares in 1994, compared with 1991-1993 in which no SAV was mapped (Tables 6 and 7). All the SAV in this segment in 1994 was classified as moderate (Table 8) and occurred in Swanson Creek (Figure 19; Appendix B, Map 49). There was no ground-truth information for RET1 in 1994.
In the Lower Patuxent River segment (LE1), the amount of SAV decreased from 0.99 hectares reported in 1993, to 0.0 hectares reported in 1994 (Tables 6 and 7; Figure 19). In 1994, the EPA and the Citizens surveyed LE1 sites and reported Z. palustris, R. maritima, M. spicatum, and P. pectinatus (Appendices B and D, Maps 60, 61, 70, and 71). Specifically, Z. palustris was reported from Battle and Osbourne creeks, and Petersons Point, on the north shore; V. americana and P. pectinatus were also reported from Battle Creek; Z. palustris and R. maritima were reported from Cuckold Creek, and M. spicatum and P. pectinatus from Green Holly Pond, both on the south shore.
The Nanticoke (ET6), Wicomico (ET7), and Pocomoke (ET10) river segments remained unvegetated in 1994, as in the years 1991-1993 (Tables 6 and 7). There was no ground-truth data for these segments in 1994.
SAV declined in both in the Manokin (ET8) and Big Annemessex rivers (ET9) in 1994 (Tables 6 and 7; Appendix B, Maps 84, 85, 92, and 93). In the Manokin River segment (ET8) there was an increase in SAV each year until 1994, up from 114.29 hectares in 1991 (Tables 6 and 7). In 1994, there was a decrease to 66.63 hectares from the four-year high level of 156.46 hectares of SAV reported in 1993 (Tables 6 and 7). There was a similar pattern in the Big Annemessex River segment (ET9). SAV increased each year from 175.54 hectares in 1991 until 1994, which had 161.79 hectares, compared with the four-year high level of 185.62 hectares observed in 1993 (Tables 6 and 7).
In the Manokin River segment (ET8), decreases in SAV occurred in three quads, primarily in Big Sound; Fishing and Goose creeks; and Drum Point Cove (Figure 20; Appendix B, Maps 84, 85, and 93). Also, SAV was absent from Letter Cove in 1994 (Map 92), but was present in Mine Creek and Laws Thorofare (Maps 84 and 93). In the Big Annemessex River segment (ET9) most of the SAV occurred in Crane, Fords, Flatland, and Shirtpond Coves; and in Acre, Daugherty, and Jones creeks (Appendix B, Map 93). In both these segments from 1991-1994 , most of the SAV was classified as moderate and sparse with little to no SAV classified as dense or very sparse (Table 8; Appendix E). In 1994 there was ground-truth data from ET8 only: R. maritima was reported from sites on the north shore of the Manokin River, in Fishing and Big Sound creeks, and in Laws Thorofare (Appendices B and D, Map 84).
In the Tangier Sound segment (EE3) in 1994, there was a decrease of SAV, and the level reported was the lowest in the four years, 1991-1994 (Tables 6 and 7). There were 4,575.39 hectares of SAV in 1994, compared with 6,015.59 hectares of SAV in 1993; 5,783.20 hectares in 1992; and 5,427.74 hectares in 1991 (Tables 6 and 7). There was also a decline in the percentage of SAV classified as dense and moderate over the four years. In 1991, 59% of SAV was classified as dense; whereas, only 24% was dense in 1994 and the percentage of SAV in classes 3 and 4 combined decreased from 80% in 1991 to 55% in 1994 (Table 8; Appendix E). SAV was present mainly in the Honga River; the eastern side of Smith and Tangier islands; the area between Great Fox Island and Cedar Island; and Big Marsh (Figure 21; Appendix B, Maps 63, 73, 74, 82, 83, 84, 91, 92, 93, 99, 100, 101, 107, 108, and 109). The majority of the decline from 1993 occurred in eight quadrangles: Honga (Map 73) - 326.99 hectares; Bloodsworth Island (Map 83) - 226.12 hectares; Kedges Straits (Map 91) - 92.66 hectares; Great Fox Island (Map 100) - 319.93 hectares; Crisfield (Map 101) - 161.16 hectares; Tangier Island (Map 107) - 71.59 hectares; Terrapin Sand Point (Map 92) - 59.33 hectares; and Parksley (Map 109) - 103.38 hectares (Table 7). SAV decreased on the western shore of the Honga River; in Okahanikan, Piney Island, and Hopkins coves; at Hope Point South; at South Marsh Island; in Plungers and Back coves; in Sheepshead Harbour; at Cedar, Janes, Smith, Thorofare, Goose, Tangier, and Jacks islands; at Simpson Point; and at Byrds Marsh. SAV was absent in 1994 in Tigs and Great coves; on the western side of Little Deal Island; and at James, Big, and Jobes islands. In 1994, VIMS reported R. maritima in the Honga River (Appendices B and D, Maps 73 and 74).
Overall, the Potomac River had a 32% decline in SAV since 1991 (Tables 6 and 7). Altogether in the Potomac River (LE2, RET2, TF2), the total amount of SAV decreased from 3,595.84 hectares in 1991; to 3,010.18 hectares in 1992; to 2,819.7 hectares in 1993; and to 2,432.01 hectares reported in 1994 (Tables 6 and 7).
In 1994, the Lower Potomac River segment (LE2) had a 67% increase over the 1991 level of 83.31 hectares (Tables 6 and 7). In segment LE2, the amount of SAV increased from 57.75 hectares of SAV reported in 1993, to 139.52 hectares of SAV reported in 1994 (Tables 6 and 7). In 1994, 68% of the total coverage of SAV was dense, 9% was moderate, 18% was sparse, and 5% was very sparse (Table 8; Appendix E). This was a 79% increase of SAV coverage in density class 4 from the 1991 level of 38% (Appendix E). Most of the changes occurred in Cuckold Creek (Map 67) and in the Wicomico River (Map 68) (Figure 22). This was the first time SAV was indicated from aerial photography for Maps 68 and 77 since 1985 and 1984, respectively (Orth et al., 1986, 1987, 1989, 1991). Several beds were noted in Machodoc, Rosier, and Goldman creeks, and below Lower Cedar Point (Maps 66 and 67). New beds were seen in the Wicomico River from Budds Creek to Bluff Point on the eastern side from below Stoddard Point to Rock Point on the western side, and in St. Catherine Sound (Appendix B, Maps 68, 77, and 162).
In 1994, the Patuxent River Park survey reported M. spicatum, Z. marina, Z. palustris, E. canadensis, and P. perfoliatus in Cuckold Creek on the north shore; Citizens reported M. spicatum, P. perfoliatus, and Z. palustris in Popes Creek, and Z. palustris in Lower Machodoc Creek on the south shore (Appendices B and D, Maps 67, 76, and 78).
In the Middle Potomac River segment (RET2), SAV decreased from 1,349.09 hectares reported in 1993 to 1,310.23 hectares in 1994 (Tables 6 and 7). This also is a decrease from the 1991 level (1,468.34 hectares) and from the four-year high 1992 level (1,551.67 hectares) (Tables 6 and 7). The percentage of SAV classified as dense, however, increased in 1994 to the four-year high of 88% (Table 8; Appendix E). SAV was located in Maps 47, 55, 56, 57, 58, 64, 65, 66, and 67 (Figure 23; Appendix B).
SAV was abundant in the mainstem Potomac River; in Chopawamsic, Aquia, Nanjemoy, Burgess and Goose creeks; and in the Port Tobacco River (Figure 23). Some decreases occurred on the eastern side of the mainstem, mainly on the Widewater quadrangle (Map 55). New SAV beds were located on the Passapatanzy quadrangle (Map 64) at Pratts and Marlboro Points, and Potomac Creek. SAV also increased in Accokeek Creek, a tributary of Potomac Creek (Figure 23; Map 64).
In 1994, the USGS, VIMS, and Citizens' surveys reported ground-truth information for RET2: M. spicatum, H. verticillata, H. dubia, V. americana, P. perfoliatus, P. pectinatus, C. demersum, N. minor, and N. guadalupensis were reported from numerous sites along both shores; H. verticillatta was reported, usually with other species, from the TF2 line, to Potomac Creek on the south shore, and to the Port Tobacco River on the north shore (Appendices B and D, Maps 47, 55, 57, 64, and 66).
The Upper Potomac River segment (TF2) SAV distribution decreased over the past four years. In segment TF2, 982.26 hectares of SAV were reported in 1994 compared with 1,412.86 hectares in 1993; 1,412.41 hectares in 1992; and 2,044.19 hectares in 1991 (Tables 6 and 7). The percentage of SAV classified as dense decreased from 1991, the year with the highest percentage (78%); however, all three remaining years had over 70% dense SAV (Table 8; Appendix E).
SAV was located in Maps 28, 29, 34, 39, 40, 47, and 48 (Appendix B). Decreases in SAV levels occurred on both sides of the Potomac River mainstem (Figure 23). The decline was visible from Piscataway Creek (Map 40) to Chicamuxen Creek (Map 48) on the eastern side (Figure 23). On the western side of the Potomac, SAV decreases occurred from below Woodrow Wilson Memorial Bridge to Hog Island (Map 34), and from Neabsco Creek to Quantico Creek (Map 47) (Figure 23). SAV was totally absent from the Port Tobacco quadrangle (Map 161) in 1994 for the first time since 1984 (Figure 23) (Orth et al., 1985). Some increases were seen in the Occoquan River and in Belmont Bay (Figure 23; Map 39).
In 1994, ground-truth data from the USGS for TF2 cited M. spicatum, V. americana, H. verticillata, H. dubia, C. demersum, N. guadalupensis, and N. minor from numerous locations along both shores; H. verticillata was reported, usually with other species, extending from D.C. in the north to the RET2 boundary in the south (Appendices B and D, Maps 28, 29, 34, 39, 40, 47, and 48).
In the Lower Central Chesapeake Bay segment (CB5) in 1994, the amount of SAV decreased from 5,006.78 hectares of SAV reported in 1993, to 3,533.27 hectares (Tables 6 and 7). This was also the lowest level of the 1991-1994 period (Tables 6 and 7). The percentage of dense SAV in 1994 also decreased from 1991 when 48% of SAV was classified as dense, although 1992 was the lowest (17%) (Appendix E). In 1994, only 21% of SAV was classified as dense, 24% was moderate, 47% was sparse, and 8% was very sparse (Table 8; Appendix E). However, the percentages of SAV in classes 3 and 4 combined for each year show 1994 (45%) increased over 1993 (37%) (Appendix E).
SAV beds were abundant at Ingram Cove; in Prentice, Dividing, Henry, Indian, and Dymer creeks; in Little and Fleets bays; and at Goose Island (Figure 24; Appendix B, Maps 82, 83, 91, 99, 100, 106, 107, 112, and 179). Decreases occurred at Adam, Holland, Spring, and Thorofare islands (Maps 83 and 100); in Johnson, Pry, Frog Point, Lighting Knot coves (Map 91); and at Dameron Marsh (Map 106). A decrease of 671.14 hectares occurred in the Ewell quadrangle (Map 99; Table 7), primarily at Smith Island, Hog Neck, Tyler Creek, and South Point Marsh. SAV was also absent in 1994 from the western side of Tangier Island (Figure 24).
In 1994 all ground-truth data was reported from the western shore of segment CB5, by the EPA and Citizens: Z. palustris and R. maritima were reported at one site near Drum Point, north of the mouth of the Patuxent River; R. maritima and Z. marina were reported at numerous sites in Fleets Bay and in Ingram Bay at the mouth of the Great Wicomico River; R. maritima was reported at the mouth of Prentice Creek (Appendices B and D, Maps 71, 106, and 112).
The amount of SAV decreased in the Rappahannock River (LE3, RET3, TF3) in 1994 in LE3, the lower Rappahannock River, the only segment to have SAV (Tables 6 and 7).
The Upper Rappahannock River segment (TF3) and Middle Rappahannock River segment (RET3) had no SAV reported in 1991-1994 (Tables 6 and 7; Figure 25), nor was there any ground-truth data reported in 1994 for these two segments.
In the Lower Rappahannock River segment (LE3), the amount of SAV decreased from the four-year high of 413.47 hectares reported in 1993, to 196.51 hectares of SAV reported in 1994 (Tables 6 and 7). This was also lower than the 1991 level of 314.78 hectares and the 1992 level of 343.37 hectares (Tables 6 and 7). The percentage of SAV classified as dense also decreased each year since 1991, from 30% that year to 2% in 1994 (Appendix E). The percentage of SAV classified as moderate underwent a similar decrease after 1991, from 25% that year to 6% in 1994 (Appendix E). In 1994, 93% of the remaining SAV fell in the very sparse and sparse classes combined (the 0-40% coverage range) (Appendix E). In fact, the very sparse class had the largest increase, from 0.0% in 1991 to 42% in 1994 (Appendix E).
In this segment (LE3), many of the 1994 beds were reduced in size compared with 1993 (Figure 25). A major decline of SAV beds occurred in both the Rappahannock and Piankatank rivers. Only seven beds were seen in the Rappahannock River, at Carter and Mosquito creeks, Windmill Point, and Parrot Island (Maps 111, 117, and 118). The Piankatank River had only one bed in 1994 (Map 118). SAV also decreased in Mosquito Creek, Hills Bay, and Milford Haven (Maps 118 and 123). SAV was present in 1994 at Gwynns Island (Maps 118 and 123), and in the Corrotoman River (Map 111), but was absent altogether in the Eastern Branch of Corrotoman River.
In 1994, R. maritima and Z. marina were reported from LE3 by VIMS; R. maritima was reported from the Corrotoman River and from Carter Creek on the north shore; Z. marina and R. maritima were reported from the mouth of the Piankatank River and the western shore of Gwynns Island (Appendices B and D, Maps 111 and 118 ).
In the Western Lower Chesapeake Bay segment (CB6), there was a decrease in SAV from 756.69 hectares of SAV reported in 1993 to 592.33 hectares of SAV reported in 1994, but this was still higher than the 1991 four-year low of 552.82 hectares (Tables 6 and 7). The percentage of SAV classified as dense decreased each year after 1991, when there was 55%, compared with 1994, when there was 10% (Table 8; Appendix E). The percentages of SAV in classes 1, 2, and 3 increased from 1991-1994 (Appendix E).
In the Western Lower Bay, SAV beds were abundant from New Point Comfort to north of Horn Harbor at Potato Neck (Figure 26; Appendix B, Map 132). Beds were also present at Windmill Point and Gwynn Island as in 1993 (Figure 26; Appendix B, Maps 118, 123, 177, and 178). Most of the decline in acreage for CB6 occurred in the Mathews quadrangle (Map 123). Mathews had 146.32 hectares less in 1994 than in 1993 (Table 7). The apparent decreases were at Milford Haven, The Hole in the Wall, Whites Creek, and Winter Harbor.
In 1994, VIMS reported groundtruth data from a few sites on the western boundary of CB6; Z. marina was reported both at Windmill Point and at Gwynn Island; R. maritima and Z. marina were reported from The Hole In The Wall, south of Gwynn Island (Appendices B and D, Maps 118 and 123).
In the Eastern Lower Chesapeake Bay segment (CB7), there was a decrease in SAV, from the four-year high of 4,183.80 hectares of SAV reported in 1993, to 3,748.74 hectares of SAV reported in 1994, although this was still an increase over the four-year low 1991 level of 3,724.53 hectares (Tables 6 and 7). The percentage of SAV classified as dense decreased each year from 1991 to 1994 (41% to 23%); whereas all the other three classes increased from 1991 levels (Appendix E).
Large beds persisted at the mouth of Cherrystone Inlet near Cape Charles and at the mouths of Mattawoman, Hungars, Nassawadox, Occohannock, Craddock, Nandua, Pungoteague, Onancock, and Chesconessex creeks (Figure 27; Appendix B, Maps 108, 113, 114, 119, 124, 133, 134, and 142). Although some creeks continued to have large beds at the mouth, they showed a reduction in SAV in other areas of the creeks: Nassawadox, Church, Hungars, Mattawoman, Onancock, Back, Nandua, and Craddock creeks. Large, dense beds also occurred at the Big Marsh area near Chesconessex Creek (Map 108). Elliotts Creek (Map 142) and Cape Charles (Map 133) were the only quadrangles which showed increases in this segment (Map 142) (Table 7). There was no SAV from Pond Drain below Elliotts Creek (Map 142), to Fisherman Island at the mouth of Chesapeake Bay. SAV beds also were mapped at Cod Harbor of Tangier Island and at Watts Island (Map 107).
In 1994, the Citizens' survey reported R. maritima at Nassawadox Point and Nassawadox Creek; VIMS reported R. maritima and Z. marina from Cherrystone Inlet (Appendices B and D, Maps 124 and 133).
In the Mobjack Bay segment (WE4), there was a slight decrease in SAV from 4,635.34 hectares reported in 1993 to 4,592.67 hectares reported in 1994, but this was still higher than the 1991-1992 levels (Tables 6 and 7). The percentage of SAV classified as dense in segment WE4 increased from 54% in 1991 to 71% in 1994 (Appendix E).
SAV beds were abundant along the entire shoreline of Mobjack Bay, as well as in the lower reaches of the tributaries: Severn, Ware, North, East, Poquoson, York, and Back rivers. The Mobjack Bay area continued to harbor some of the more extensive SAV beds on the western shore of the lower Chesapeake Bay (Figure 28, Appendix B, Maps 122, 123, 131, 132, 140, 141, and 147).
In 1994, Z. marina and R. maritima were reported by VIMS and Citizens' surveys from Maps 131, 132, and 140 in segment WE4 (Appendices B and D). Specifically, R. maritima alone was reported from the East River on the north shore of Mobjack Bay; Z. marina alone was reported from the Ware River on the south shore of Mobjack Bay; R. maritima and Z. marina together were reported from the north shore of Mobjack Bay adjacent to the East River and Pepper, Davis, and Harper creeks; R. maritima and Z. marina together were also reported from the south shore of Mobjack Bay (Ware Neck to the Guinea Marshes), from the north shore of the mouth of the York River (Big Island to the Perrin River), and from the south shore of the mouth of the York River (the Goodwin Islands) (Appendices B and D, Maps 131, 132, and 140).
Altogether, in the York River (LE4, RET4, TF4), there was a slight increase of SAV reported for 1994 and that was from LE4, the only segment of the three to have any SAV (Tables 6 and 7).
The number of hectares of SAV in the Lower York River segment (LE4) increased slightly each year from 65.64 hectares in 1991, to 66.79 hectares in 1992, to 76.55 hectares in 1993, to 78.29 hectares in 1994 (Tables 6 and 7). This segment continued to have the majority of its SAV classified as dense from 1991-1994 and although there was a slight decrease from the 1993 level of 86% to 77% in 1994, this was still higher than the 1991 level of 60% (Appendix E). There was no SAV classified as moderate in 1994 (Appendix E).
In the lower York River (LE4), sparse SAV was documented for a portion of the south shore of the York River, downstream from Yorktown, for the second year in a row (Figure 29; Appendix B, Maps 139 and 140). Dense SAV beds were located principally along the north shore from the Coleman Bridge to the mouth of the river (Appendix B, Maps 131, 139, and 140). SAV beds were absent upstream of the Coleman Bridge along the south shore except for three small beds (Figure 29; Appendix B, Map 139, beds AA1, BA2, and CA1). SAV persisted along the south shore after being documented in 1993 for the first time since 1971, from Yorktown to the Coast Guard pier (Orth and Gordon, 1975; et al, 1994).
In 1994, Z. marina was noted by VIMS staff (Maps 139 and 140, Appendices B and D). Specifically, Z. marina was reported on the north shore of the York River at Gloucester Point, east of the Coleman Bridge, and along the south shore adjacent to the U.S. Naval Supply Center and to Yorktown (Appendices B and D, Maps 139 and 140).
The Upper York segment (TF4) and Middle York segment (RET4) reported no SAV from 1991-1994 (Tables 6 and 7; Figure 29). There was no ground-truth information reported for these two segments in 1994.
There was a slight increase of SAV in the James River (LE5, RET5, TF5) each year from 1991-1994 (Tables 6 and 7). SAV was mapped only from the Lower James (LE5).
SAV increased in the Lower James River segment (LE5), from 4.01 hectares reported in 1993, to 6.10 hectares reported in 1994 Tables 6 and 7). The percentage of SAV in this segment in 1994 that was classified as dense decreased from 100% in 1993 to 0% in 1994, whereas 100% of the SAV in 1994 was classified as moderate, the same as in 1991-1992 (Table 8; Appendix E). The SAV in this segment was located in a single bed in the mainstem of the river at the mouth of Hampton Creek adjacent to the Veteran's Hospital, as it was in 1991-1993, and continued to remain the only SAV mapped from aerial photography in the James River (Figure 30). This bed consists of Z. marina as reported by VIMS (Appendices B, C, and D, Map 147). Citizens survey an unknown species at the mouth of Skiffes Creek (Appendix B and D, Map 139).
The Upper James River segment (TF5) and Middle James River segment (RET5) reported no SAV for 1991-1994 (Tables 6 and 7, Figure 30). There was no ground-truth information reported from either of these two segments in 1994.
The Mouth of Chesapeake Bay segment (CB8) had an increase of SAV from 21.22 hectares in 1993 to 42.65 hectares in 1994, the highest level from 1991-1994 (Tables 6 and 7). There was no SAV classified as dense from 1991-1994, nor was there any classified as moderate in 1994, which was a decline from 1993 when 33% was moderate (Appendix E). In 1994, 69% of the SAV was classified as sparse, and 31% was very sparse (Table 8; Appendix E).
SAV was present in Linkhorn Bay for the first time since 1990 on both Cape Henry and Princess Anne quadrangles (Figure 31; Appendix B, Maps 152 and 157) (Orth et al., 1991). SAV was also abundant in Broad Bay (Figure 31, Map 152). VIMS and Citizens' surveys found R. maritima and Z. marina in Broad Bay, and VIMS staff noted R. maritima in Linkhorn Bay (Appendices B and D, Maps 152 and 157).
SAV in the Chincoteague section increased each year from 1991 to 1994 (Tables 6 and 7). There was a 1,371.90 hectares (50%) increase in this four year period.
There were 4,117.53 hectares of SAV identified from the Eastern Shore of Virginia and Maryland in 1994 compared with 3,576.57 hectares reported in 1993 (Tables 6 and 7). Chincoteague and Sinepuxent bays had 3,979.31 hectares, and a small amount (138.22 hectares) was present in Isle of Wight and Assawoman bays ((Tables 5, 6, and 7; Figure 32; Appendix B and C, Maps 166, 167, 168, 170, 172, 173, 174, and 175). Most of the SAV in Chincoteague and Sinepuxent bays was located along the eastern sides of both bays behind Assateague Island, the barrier island that forms these bays. Several beds were located along the eastern side of Isle of Wight and Assawoman bays, behind Fenwick Island, the barrier island which forms these bays. In this segment in 1994, 55% of the total coverage was mapped as dense (class 4), 31% as moderate (class 3), 12% as sparse (class 2), and 1% as very sparse (class 1) (Table 9; Appendix E). The density distribution has remained somewhat similar from 1991 to 1994: in all four years the largest percentage of SAV was classified as dense, 54% or above; that classified as very sparse was 5% or under each year (Table 9, Appendix E). The percentages for sparse and moderate SAV were more variable (Table 9, Appendix E). Sparse SAV ranged from 4% and 5% in 1991 and 1992, respectively, to 26% in 1993, and then 12% in 1994 (Table 9). Moderate SAV ranged from 24% in 1991, 35% in 1992, 17% in 1993, and 31% in 1994 (Table 9).
The Citizens' survey found both Z. marina and R. maritima throughout Chincoteague, Sinepuxent, and Assawoman bays. The Ocean Pines Boat Club also noted these two species in Assawoman Bay (Appendices B and D, Maps 166, 167, 168, 170, 172, 173, 174, and 175).