Invertebrates and Plants
Invertebrates and plants are among the most ubiquitous and abundant macroscopic organisms in aquatic ecosystems; they dominate most habitats in both diversity and biomass and play central roles in aquatic food webs. Plants regulate and create habitats for a wide array of organisms (Cooke et al. 2005). Snail grazing and bivalve filtering profoundly alter habitats and communities (Harvey and Hill 1991; Vaughn and Hakenkamp 2001). Aquatic habitats in North America support extremely diverse floras and invertebrate faunas; groups such as crayfishes and freshwater mollusks reach their highest worldwide diversity here. Crayfishes are important economically for human food, fishing bait, and the aquarium pet trade industry (Nielsen and Orth 1988; Huner 1997). Freshwater mussels have been exploited heavily in North America since at least the mid-1800s for freshwater pearls, button production, and currently for cultured-pearl bead nuclei (Anthony and Downing 2001).