Paul E. Fell

Rates, Patterns, and Impacts of PHRAGMITES AUSTRALIS Expansion and Effects of Experimental PHRAGMITES Control on Vegetation, Macroinvertebrates, and Fish within Tidelands of the Lower Connecticut River

Phragmites expansion rates (linear at 1–3% yr−1) and impacts of this expansion on high marsh macroinvertebrates, aboveground production, and litter decomposition fromPhragmites and other marsh graminoids were studied along a polyhaline to oligohaline gradient. These parameters, and fish use of creeks and high marsh, were also studied inPhragmites control sites (herbicide, mowing, and combined herbicide/mow treatments).Phragmites clones established without obvious site preferences on oligohaline marshes, expanding radially. At higher salinities,Phragmites preferentially colonized creekbank levees and disturbed upland borders, then expanded into the central marsh. Hydroperiods, but not salinities or water table, distinguishedPhragmites-dominated transects. Pooled samples ofPhragmites leaves, stems, and flowers decompose more slowly than other marsh angiosperms;Phragmites leaves alone decompose as or more rapidly than those of cattail. AbovegroundPhragmites production was 1,300 to 2,400 g m−2 (about 23% of this as leaves), versus 600–800 g m−2 for polyhaline to mesohaline meadow and 1,300 g m−2 for oligohaline cattail-sedge marsh. Macroinvertebrates appear largely unaffected byPhragmites expansion or control efforts; distribution and densities are unrelated to elevation or hydroperiod, but densities are positively related to litter cover. Dominant fish captured leaving flooded marsh wereFundulus heteroclitus andAnguilla rostrata; both preyed heavily on marsh macroinvertebrates.A. rostrata andMorone americana tended to be more common inPhragmites, but otherwise there were no major differences in use patterns betweenPhragmites and brackish meadow vegetation. SAV and macroalgal cover were markedly lower within aPhragmites-dominated creek versus one withSpartina-dominated banks. The same fish species assemblage was trapped in both plus a third within the herbicide/mow treatment. Fish biomass was greatest from theSpartina creek and lowest from thePhragmites creek, reflecting abundances ofF. heteroclitus. Mowing depressedPhragmites aboveground production and increased stem density, but was ineffective for control.Phragmites, Spartina patens, andJuncus gerardii frequencies after herbicide-only treatment were 0.53-0.21; total live cover was <8% with a heavy litter and dense standing dead stems. After two growing seasonsAgrostis stolonifera/S. patens/J. gerardii brackish meadow characterized most of the herbicide/mow treatment area;Phragmites frequency here was 0.53, contributing 3% cover. Both values more than doubled after four years; a single treatment is ineffective for long-termPhragmites control.

Does invasion of oligohaline tidal marshes by reed grass, Phragmites australis (Cav.) Trin. ex Steud., affect the availability of prey resources for the mummichog, Fundulus heteroclitus L.?

Reed grass (Phragmites australis (Cav.) Trin. ex Steud.) has invaded large areas of tidal marsh along the lower Connecticut River and often occurs as a monoculture. Tidal marsh invertebrates (snails, amphipods and isopods) were common to abundant in reed grass-dominated regions, as well as in areas covered by typical tidal marsh vegetation at four sampling stations set up along the salinity gradient. This finding suggests that reed grass marshes provide suitable physical habitat and usable food resources for these semiaquatic detritus/algae feeders. Mummichogs (Fundulus heteroclitus L.) were caught on the high marsh during daylight high tides using Breder traps and an analysis of their gut contents was made. When daylight tides were high enough to cover the marsh surface, mummichogs moved up onto the marsh and fed extensively on marsh invertebrates, both in reed grass marshes and reed grass-free marshes. Such foraging appears to represent a direct trophic link between the marshes and adjacent estuarine waters. Even when tides were not high enough to flood the marsh surface, mummichogs moved into the tidal creeks that course through reed grass marshes and largely reed grass-free marshes and foraged there. With respect to macroinvertebrate populations and mummichog foraging, the reed grass marshes appear to be functioning in essentially the same ways as nearby marshes not invaded by this plant, at least in the short term.

Gut contents of common mummichogs, Fundulus heteroclitus L., in a restored impounded marsh and in natural reference marshes

We examined the gut contents of mummichogs, Fundulus heteroclitus L., entering and leaving ditches in three marsh regions within the Barn Island Wildlife Management Area in Connecticut: a restored impounded valley marsh, a marsh below the impoundment dike (Headquarters Marsh), and an unimpounded valley marsh (Davis Marsh). On the Headquarters Marsh and at certain times on the other two marshes, fish entered the ditches on the flooding tide with relatively little food in their guts and left them on the following ebbing tide with considerably more food in their guts. Since the high tides did not flood the surface of the high marsh, it appears that the ditches are important foraging areas. Major components of the gut contents were detritus, algae, amphipods, tanaids, copepods, and insects. During the summer, fish in the restored impounded marsh consumed less food per unit body weight than did fish inhabiting the other marsh regions.

Comparison of fish and macroinvertebrate use ofTypha angustifolia, Phragmites australis, and treatedPhragmites marshes along the lower Connecticut River

Since 1965 large areas of lower Connecticut River tidelands have been converted from high diversity brackish meadow andTypha angustifolia marsh to near monocultures ofPhragmites australis. This study addresses the impact ofPhragmites invasion on fish and crustacean use of oligohaline high marsh. During spring tides from early June through early September 2000, fishes and crustaceans leaving flooded marsh along 3 km of the Lieutenant River, a lower Connecticut River tributary, were captured with Breder traps at 90 sites, equally distributed amongPhragmites, Typha, and treated (herbicide and mowing)Phragmites areas. Pit traps, 18 per vegetation type in 2000 and 30 each inPhragmites andTypha in 2001, caught larvae and juveniles at distances of up to 30 m into the marsh interior. There were no significant differences in fish species compositions or abundances among the vegetation types. Size distributions, size specific biomasses, and diets ofFundulus heteroclitus, the numerically dominant fish, were also similar. The shrimpPalaemonetes pugio was more abundant inPhragmites than in other types of vegetation, whereas the fiddler crabUca minax was least numerous inPhragmites. Mean numbers ofF. heteroclitus andP. pugio caught per site event were positively correlated with increasing site hydroperiod. Significantly moreF. heteroclitus were captured along the upper reach of the river where marsh elevations were lower than farther downstream. MoreF. heteroclitus and fewerP. pugio andU. minax were captured during the day than at night. A relatively small number of larval and juvenileFundulus sp. were captured in pit traps, but consistently fewer inPhragmites than inTypha, suggesting thatTypha and brackish meadow marshes may provide better nursery habitat. Vegetation was sampled along a 30 m transect at each trap site in 2000. Plant species diversity was greatest in treatedPhragmites areas and lowest inPhragmites sites.

Distribution and abundance of macroinvertebrates on certain connecticut tidal marshes, with emphasis on dominant molluscs

The distribution of macroinvertebrates on Connecticut tidal marshes corresponds well with that reported for other marshes along the Atlantic and Gulf coasts of the United States. The greatest densities and biomass of the ribbed mussel,Geukensia demissa, were found on marshes in the central and western part of the state where both the annual production ofSpartina alterniflora and tidal range are large. *** DIRECT SUPPORT *** A01BY019 00011

Re-establishment of Melampus bidentatus (Say) and other macroinvertebrates on a restored impounded tidal marsh: comparison of populations above and below the impoundment dike

Abstract Macroinvertebrates were studied on an impounded marsh in Stonington, Connecticut, that has converted from a Typha-dominated system to one with typical tidal marsh vegetation during the 12 yr following the re-introduction of tidal flushing. Regions of marsh above and below the impoundment dike were compared in order to assess the extent to which tidal marsh invertebrates have recolonized the restored region. Marshes below the impoundment dike consist of two types: marshes that are dominated by Spartina patens (Ait) Muhl and have remained relatively stable for several decades and marshes in which large areas have changed form nearly pure stands of S. patens to stunted Spartina alterniflora Loisel. and forbs during the last 40 yr coincident with an increase in sea level relative to the marsh surface. In most of the areas occupied by S. alterniflora , varying amounts of S. patens persist. Melampus bidentatus Say and other tidal marsh invertebrates have become established on the restored impounded marsh and occur at moderate densities on the stable bayfront marshes and in some areas of the bayfront marshes that have exhibited dramatic vegetational change. The mean density of Melampus on the restored marsh was 83 · 0.25 m −2 , that on the S. patens-dominated bayfront marshes was 98 · 0.25 m −2 and that on the changing bayfront marshes was 117 · 0.25 m −2 . Within each marsh region, snail density varied in relation to plant cover and elevation. The size structure of the Melampus populations in different marsh regions differed. On the restored marsh 83% of the snails exceeded 8 mm in shell length, while on the S. patens-dominated marshes 95% of the snails were ⪕8 mm. Because of these differences in snail size, the mean shell-free biomass of Melampus was 2 x greater on the restored marsh (1.24 g dry wt · 0.25 m −2 ) than on the S. patens-dominated marshes (0.63 g dry wt · 0.25 m −2 ). The mean of Melampus on the changing bayfront marshes was 1.01 g dry wt · 0.25 m −2 .

Population dynamics of the estuarine sponge, Halichondria sp., within a New England eelgrass community

Abstract The population dynamics of Halichondria sp. within an eelgrass bed in the lower Mystic Estuary, Connecticut, were examined during a 2-yr period. Large numbers of larva-derived specimens develop on the eelgrass during the summer, and many of these sponges become sexually reproductive, further increasing the size of the population. However, mortality is high, and at the end of the summer only a relatively small sponge population remains. Sexual reproduction by larva-derived specimens of Halichondria occurs primarily after breeding by the parental generation has declined. The larva-derived sponges grow rapidly, and the percentage of specimens containing large, female reproductive, elements increases with specimen size. Halichondria exhibits an opportunistic life strategy with a high rate of turnover.

Evaluation of tidal marsh restoration: comparison of selected macroinvertebrate populations on a restored impounded valley marsh and an unimpounded valley marsh within the same salt marsh system in Connecticut, USA

Macroinvertebrates were examined on an impounded valley marsh in Stonington, Connecticut, that has changed from aTypha-dominated system to one with typical salt-marsh vegetation during 13 years following the reintroduction of tidal exchange. Animal populations on this restored impounded marsh were evaluated by comparing them with populations on a nearby unimpounded valley marsh of roughly the same size. Populations of the high marsh snail,Melampus bidentatus Say, were quantitatively sampled along transects that extended from the water-marsh edge to the upland; those of the ribbed mussel,Geukensia demissa Dillwyn, were sampled in low marsh areas on transects along the banks of creeks and mosquito ditches. The occurrence of other marsh invertebrates also was documented, but their abundance was not measured. The mean density ofMelampus was 332±39.6 SE/m2 on the restored impounded marsh and 712±56.0 SE/m2 on the unimpounded marsh. However, since snails were larger on the restored impounded marsh, the difference in snail biomass was less pronounced than the difference in snail density. MeanMelampus biomass was 4.96±0.52 SE g dry wt/m2 on the restored impounded marsh and 6.96±0.52 SE g dry wt/m2 on the unimpounded marsh. On the two marshes, snail density and biomass varied in relation to plant cover and other factors. The density and biomass ofGeukensia at the edge of the marsh were comparable on the restored impounded and unimpounded marshes. Mean mussel densities ranged from 80 to 240/m2 and mean mussel biomass varied from 24.8–64.8 g dry wt/m2 in different low marsh areas. In contrast, below the impoundment dike, meanGeukensia density was 1100±96.4 SE/m2 and meanGeukensia biomass was 303.6±33.28 SE g dry wt/m2. A consideration of all available evidence leads to the conclusion that the impounded marsh is in an advanced phase of restoration.

REPRODUCTION AND DEVELOPMENT OF HALICHONDRIA SP. IN THE MYSTIC ESTUARY, CONNECTICUT

1. A description of gametogenesis and embryonic development in Halichondria sp. is presented.2. Halichondria sp. exhibits an incomplete gonochorism in which some specimens produce either eggs or sperm and others produce both. When the sexes are separate, the sex ratio is about 1 : 1:3. In the Mystic Estuary, Connecticut, the reproductive period of postdormant specimens extends from May into July, while the reproductive period of postlarval specimens begins in July and continues at least into October. Since the reproductive periods of postdormant and postlarval specimens are separated, it appears that reproduction is, to a large extent, under endogenous control.

Low-salinity tolerance of and salinity-induced dormancy in the estuarine sponge Microciona prolifera (Ellis et Solander) under long-term laboratory culture

Abstract Explants of Microciona prolifera (Ellis et Solander), maintained in long-term laboratory culture at 20°C, were transferred to different low salinities at different rates and for different periods of time. Explants transferred directly from 30%. seawater to 20%. seawater remained healthy and active. Following direct transfer from 30%. seawater to 15%. seawater, the explants underwent dormancy for several days after which they resumed normal activity. During the dormant period, pumping ceased and subdermal spaces, canals and oscula disappeared. Direct transfer from 30%. seawater to 10%. seawater was lethal. Progressive transfer of the explants from 30%. seawater to 10%. seawater resulted in dormancy which persisted until the salinity was raised. Such dormancy was induced when the salinity was changed 5%. every day, 5%. every 3 days or 5%. in two steps every 9 days. The explants remained dormant but healthy in 10%. seawater for up to 25 days. Explants transferred progressively from 30%. seawater to 5%. seawater survived exposure to the lower salinity for up to 7 days when the change in salinity was gradual. Cold-dormant explants at 4 °C appeared to be less low-salinity tolerant than explants maintained at 20°C.