User:Hcoles1/sandbox

Freshwater bivalves are filter feeders and provide an ecological service by improving water quality in rivers and lakes. Water quality is improved by filtering out fine particles of silt, organic matter, and heavy metals in the water column to reduce turbidity.

The exact genera and species diversity cannot be determined due to the absence of data in certain areas of the world. Freshwater bivalves are endemic to the southeastern United States and the Oriental region. Hyriidae genera from South America and Australasia, restricted to Australia, Tasmania, New Zealand, New Guinea and the Solomon Islands. 40 genera in the Palearctic, 59 in the Nearctic, 23 in the Afrotropical, 51 in the Neotropical, 47 in the Oriental, 13 in the Australasian, 2 in the Pacific Ocean Islands, and 0 in the antarctic, totalling to 206 genera in the world. The 2 genera in Spaeriidae in the Pacific Ocean Islands are introduced from Hawaii. 38 genera of Unionidae are introduced into the Oriental region. 20 Unionidae, 2 corbiculidae, and mytilidae are introduced in the neotropical. 1 Dreissenidae, 1 corbiculidae, 51 unionidae are introduced in the nearctic. 26 unionidae are intorduced in the palearctic. FW bivalve fauna of Africa and South America is poorly known

Notes:

Bogan 2008

Buelow and Waltham 2020
 * Class Bivalvia -> 3 subclasses -> 5 orders -> at least 19 families have at least one representative living in FW indicating at least 14 different invasions into freshwater or separation of stream systems by vicariant events: Sphaeriidae, Corbiculidae, Unioniformes; 206 recognized genera of FW bibalves
 * Unionidae: obligate parasitic larval stage on gills, fins or the body of a particular host fish
 * 37 species in the order Unionidae are presumed extinct in North America
 * declining due to habitat destruction or modification due to the effects of dams, canalization, changes in water depth due to flow changes (water withdrawl for industry and irrigation), pollution from impervious areas from urbanization and road building, and changes in fine particle deposition; indirect effects on the fish unioniformes rely on for their obligate parasitic life stage
 * obligate freshwater organisms; entire life cycle is in freshwater
 * a mollusk without a head, have a single foot enclosing the visceral mass, two pair of gills, and sexes dimorphic. Two valves composed of calcium carbonate surrounding the body.
 * shell shape varies among families reflecting history and habitat conditions
 * bysus: a tuft of tough silky filaments by which mussels and some other bivalves adhere to rocks and other objects. (blue and zebra mussels) Thinner shelled than species living in coarse substrate. (maybe to reduce drag while attached to rocks?)


 * reduce phytoplankton levels through filter-feeding and altering nutrient levels through excretion and biodeposition.
 * limited to high temperature waters, size, population, and environmental context.
 * maybe check Blomberg et al. 2018; Pollack et al. 2012; staryer and malcolm 2007
 * supplying food or habitat for other species

Freshwater bivalves are also important in the process of nutrient cycling because they deposit organic matter in the sediment through biodeposition created from the fine particles they filter in. Organic matter can be deposited in the sediment as feces or dead matter, and depending on if the right environmental conditions are present such as anoxia, sediment denitrification can occur, releasing nitrogen back into the atmosphere. However, other organisms are unable to utilize this inorganic form of nitrogen, so freshwater bivalves can also excrete dissolved nutrients in a labile form for primary producers and consumers to assimilate. Any nutrients that were retained by the freshwater bivalve through its lifespan for building shell tissue can serve as a long-term nutrient storage in the benthos, depending on water chemistry and flow conditions.