Adopt-A-Wetland

Changing environmental conditions can be stressful to aquatic organisms, and few species (but high
abundance of animals in each species) live in the estuary. However, species composition can fluctuate with
the seasons. Generally, peak densities of estuarine fauna occur in the spring or fall, with lowest animal
density occurring during the summer due to predation and competition. Typically, biodiversity is low in the
estuary and animal populations are usually r-selected species.
Diversity of Estuarine Mud Flats
Mud flats are another habitat supporting estuarine invertebrates and fish. They are located at the edges of
the salt marsh extending out into the creeks and rivers. These areas are comprised of varying combinations
of clays, silts, or sand. Although few species dwell in this zone, the densities of animals present in the mud
are high. Polychaetes and mud snails are generally the dominant organisms found in the mud. However,
there are various assortments of predators also found (usually at high tide). These include blue crabs
(Callinectes sapidus), grass shrimp (Palaemonetes pugio), penaeid shrimp (Penaeus aztecus, P. setiferus), silversides
(Menidia spp), and killifish (Fundulus spp). As the tide changes, many fish (e.g. skates, rays, and flat fish such as
flounders, small sharks, and red drum) will congregate on the shallow waters of a mud flat feeding on many
of the animals in the area.
Blue crab. Photo credit: Jarek Tuszynski/Wikimedia Commons
44 DRAFT AUGUST 2015