Beach invertebrates of Cape Cod National Seashore: Environmental factors and the effects of off-road vehicles
Off-road vehicle (ORV) effects on invertebrates inhabiting macrophyte debris (wrack) and supratidal sands on energetic beaches in the northeastern United States were studied at Cape Cod (MA) and Fire Island (NY) National Seashores. Cores, wrack quadrats, and pitfall traps were used to sample four beaches, all having vehicle-free sections next to ORV corridors. A manipulative experiment was performed by directly driving over wrack-filled, nylon-mesh bags colonized by beach invertebrates and subjected to traffic treatments. ^ Pitfall traps at the wrackline had higher invertebrate abundances in vehicle-free than in high-traffic zones on all four beaches. Wrack abundance was higher on vehicle-free beaches. However, wrack quadrats (with intact wrack) and cores taken beneath them showed no consistent differences in invertebrate abundances in traffic and non-traffic areas. Talitrid amphipods Talorchestia longicornis and lycosid spiders Arctosa littoralis, both diurnal burrowers in supratidal bare sands as adults, were less abundant in traffic sections of beach. Other invertebrates, e.g., oligochaetes and tethinid flies (Tethina parvula), living within/beneath wrack, were not affected by traffic. ^ In the direct impact study, the tenebrionid beetle Phaleria testacea (85% larvae) was less abundant in disturbed wrack bags than in controls, while Tethina parvula (90% larvae) showed increases in disturbed wrack. Nonetheless, ORVs adversely affected invertebrates, by killing/displacing some species and by lowering the total wrack amount. Therefore, on beaches with moderate traffic levels, alternating opening/closing of adjacent beaches to vehicle traffic may allow wrack invertebrate recolonization and population recovery. ^ Wrack manipulative studies were used to isolate the influences of wrack location and proximity to dune vegetation, clump size and composition on macrofaunal assemblages. Wrack deposits were colonized primarily by wrack-associated species, including semi-terrestrial and terrestrial groups, with few dune grass or swash zone species. Across-shore location affected macrofaunal abundances and community structure, independent of wrack age, with high-tide line deposits attracting the most individuals. Some species were broadly distributed, but others preferred certain beach wrack locations. Macroinvertebrate abundance and diversity increased proportionally with clump size, with no change in density per unit wrack. Wrack substrate affected community structure, with greater species and fauna in Zostera marina and Ascophyllum nodosum than in Spartina alterniflora. ^
Biology, Ecology|Biology, Entomology|Biology, Oceanography
Jacqueline Michele Kluft,
"Beach invertebrates of Cape Cod National Seashore: Environmental factors and the effects of off-road vehicles"
Dissertations and Master's Theses (Campus Access).