Effects of landscape on macroinvertebrate assemblages in beaver-mediated wetlands, Aroostook County, Maine

Research comparing three aquatic sampling methods, a comparison of macroinvertebrate biomass and diversity in ponds between agricultural and forested areas in Aroostook County, and a review of the species of predaceous diving beetles in Maine were performed from 1993 through 1995.; I compared abundance, biomass, caloric content and non-species diversity of macroinvertebrates among 1.2 L horizontally-oriented activity trap, 1 m long drag D-frame aquatic net and 0.2 m{dollar}sp2{dollar} area cylinder samples. The mean numbers of insects/trap for 50 matched samples were greater {dollar}(Ple0.05){dollar} for a cylinder sampler and a D-frame aquatic net than in an activity trap. Number of taxa and size of taxa in samples from a cylinder sampler were more similar to sweep net samples than those from an activity trap. The cylinder sampler captured 75 genera from 7 orders of insects, the sweep net 60 genera from 6 orders, and the activity trap 35 genera from 5 orders. Activity traps captured a greater {dollar}(Ple0.004){dollar} percent of adult Coleoptera, Acariformes, and Arhynchobdellida than sweep nets that captured more Diptera, Ephemeroptera, Hemiptera, Trichoptera, Amphipoda, Gastropoda, and Bivalvia. A greater percentage of beetles than other insects were captured in activity traps as the length of time the trap was deployed increased beyond 24 hr. Ranks of fourteen ponds based on activity trap and sweep net samples were not correlated for insect abundance {dollar}(rho=-0.14),{dollar} biomass {dollar}(rho = -0.09),{dollar} or calories {dollar}(rho=-0.17).{dollar} Activity trap and sweep net samples provide different information about the aquatic macroinvertebrate assemblages inhabiting wetlands.; I compared macroinvertebrate, amphibian, and fish abundance in ponds between an area with {dollar}>{dollar} 42% agricultural land-use (AGR) and an area with {dollar}le{dollar}42% (FOR). Seven orders, 46 families, and 99 genera of macroinvertebrates were captured; 9 families and 20 genera were unique to the FOR area, and 6 families and 17 genera were unique to the AGR area. An assemblage of snails, Planorbidae; mayflies, Caenidae; and beetles, Haliplidae identified by Detrended Correspondence Analysis was characteristic of ponds from the AGR area. The mean abundance (x) of insects was greater {dollar}(Ple0.05){dollar} in the FOR area than in the AGR area; however, the number of calories of insects and Shannon-Wiener non-species diversity indices were not different between areas. Pathway analyses showed that nutrients explained different amounts of the variation in periphyton biomass and macrophyte cover within the AGR and FOR areas, and at the regional scale.; Locations, habitat descriptions, and collection dates are listed for new records of 4 genera and 12 species of predaceous diving beetles (Coleoptera: Dytiscidae) in Maine. Previously, 17 genera and 53 species of the aquatic beetle family Dytiscidae were reported from Maine.