New England salt marsh pools: Analysis of geomorphic and geographic parameters, macrophyte distribution, and nekton use

Salt marsh pools provide important habitat for nekton (fish and decapod crustaceans). Although relatively unstudied, efforts are underway to expand pool habitat through a technique known as ditch plugging. The purpose of this study was to quantify pool geomorphic and geographic characteristics, to determine distribution of vegetative cover types and nekton species, and to evaluate effects of ditch plugging on nekton use of pools.; Over 30 ditched and unditched marshes were surveyed from the Connecticut shore of Long Island Sound to southern Maine, USA. Pool density (#/ha marsh) and coverage (m2 pool/ha marsh) were over twice as great at unditched versus ditched marshes. Ditch intensity (m ditch/ha marsh) was negatively correlated to pool density and coverage.; Pool cover types surveyed at 12 marshes resulted in eight categories; “bare” (pool bottom visible) and filamentous green algae were most common. Canonical correlation analysis demonstrated that R. maritima and algal flocculations were separated by water depth, soft sediment depth, and water column nitrogen.; Pool nekton sampling using 1m2 throw traps documented 12 fish and 4 decapod species with F. heteroclitus comprising 80% of the fish catch. Species richness and density were greater in southern versus northern New England salt marshes. In contrast to other studies, fish densities were not affected by the presence of submerged aquatic vegetation (R. maritima). Data suggest that F. heteroclitus use pools as nursery habitat and as refuges from predation, selecting among pools with different environmental conditions as the season progressed and juvenile size increased.; Ditch plugging at 3 sites in the Rachel Carson National Wildlife Refuge, Maine, was evaluated for initial effects on nekton use of pools. After controlling for natural variation using the BALI (Before-After-Control-Impact) design, few nekton parameters were altered at Moody and Granite Point. Decreased species richness at Granite Point was thought due to physical barriers of ditch plugs and a 51% reduction in tidal interface. At Marshall Point, ditch plugging resulted in increased pool habitat and nekton use. Nekton occupied newly created pools within weeks, and within months new pools were not discernable from old pools in terms of nekton use.