marine bio final - estuaries

coastal plain estuary

formed when rising sea levels flood river valleys

bar-built estuary

created by sandbars or barrier islands trapping water behind them

tectonic estuary

formed by land subsidence or tectonic activity creating a basin that fills with water

fjord estuary

formed by retreating glaciers that carved deep valleys, which are then flooded by seawater

fluctuating salinity

organisms must adapt to both freshwater and saltwater conditions

tidal changes

rapid water level changes can expose organisms to predators

sediment and pollution

high sediment loads and pollutants can clog feeding structures and reduce oxygen levels

temperature variability

shallow waters can experience rapid temperatures changes

salinity gradient in estuaries

freshwater from rivers meets and miles with saltwater from the ocean. the gradient influences species diversity.

Freshwater zone

Low salinity, high diversity of freshwater species adapted to low salinity conditions

brackish zone

intermediate salinity, a decline in species diversity occurs in this zone

Marine zone

high salinity, increase in diversity with marine species adapted to higher salinity levels

physiological stress

organisms adapted to either freshwater or marine environments may struggle to osmotegulate in brackish conditions, which leads to reduced diversity

limited specialized species

fewer species have evolved to specialize in brackish environments, resulting in low diversity

environmental variability

estuaries experience fluctuations on salinity due to tides and seasonal changes, which creates a challenging condition for species survival

salinity fluctuations

rapid changes in salinity can stress organisms not adapted to such variability

pollution

estuaries often accumulate pollutants from upstream

habitat alteration

human activities like dredging and land reclamation can disrupt estuarine habitats

competition and predation

the mix of species from different environments can disrupt estuarine habitats