Estuaries — a biological point of view

Abstract

Estuaries are considered adverse environments for many living organisms because of their unstable environmental conditions. Variability in salinity, temperature and oxygen concentration of the water, diverse substrata and geomorphological structures are major contributors to increased ecological stress in estuaries. These variations contribute to the characteristic estuarine spatial and temporal changes of physico-chemical properties, which operate even at small scales.In terms of biology estuaries represent fascinating environments -transition zones between freshwater and marine biomes. Freshwater entering an estuary has a major influence on the ecology of the system, its productivity, diversity and the distribution of organisms, with a high variability of niches favouring an increase of biodiversity and biomass. Many estuarine species/organisms show broad and efficient physiological adaptations (ecotypes) in response to these environmental factors. Under locally specific conditions, even different genetic clades (groups) can be formed. Estuaries serve as vital nursery systems for many fish and unique feeding grounds for migratory birds. On the other hand, estuaries are often seriously degraded habitats, hence providing an ideal environment for combining studies on ecology, nature conservation and human impact.

Some like it hot: population-specific adaptations in venom production to abiotic stressors in a widely distributed cnidarian

“…Nematostella vectensis is a burrowing sea anemone which specializes in estuarine environments with a unique role as an infaunal predator [1]. These brackish habitats are characterized by variable daily and seasonal abiotic conditions, particularly temperature, salinity, and ultraviolet (UV) light [2][3][4][5][6]. Nematostella has a broad geographic range along the Atlantic and Pacific coasts of the USA and southern Canada where the extent of variation in environmental conditions changes by latitude or location within the estuary [1].…”

Landscape genetic structure of Scirpus mariqueter reveals a putatively adaptive differentiation under strong gene flow in estuaries

“…Estuary may be the best laboratory to reveal the interaction between divergent selection and gene flow (Bible & Sanford, 2016;McCairns & Bernatchez, 2008). It represents the transitional zone between freshwater from inland and salt water from open sea (Potter, Chuwen, Hoeksema, & Elliott, 2010;Pritchard, 1967), where various processes including physical, chemical, biological, and geological dynamics are immensely complex (Wolowicz, Sokolowski, & Lasota, 2007). The distinguishing attribute of estuaries is the impact of abiotic characteristics, such as the mixing of two water sources, the rise and fall of the tides and ocean currents.…”

Assessments at multiple levels of biological organization allow for an integrative determination of physiological tolerances to turbidity in an endangered fish species

“…This is certainly the case in the San Francisco Estuary (herein referred to as ‘Estuary’) and Sacramento–San Joaquin River Delta (herein referred to as ‘Delta’), USA, representing a paragon for such heavily influenced ecosystems ( Nichols et al , 1986 ). Estuaries are a unique ecosystem type denoted by the interface between coastal marine and riverine freshwater habitats ( Wołowicz et al , 2007 ) and provide a dynamic habitat for highly specialized and adapted species. Characteristic of estuaries are mixing zones, which originate from freshwater outflow, saltwater intrusion and a distinctive recurring ebb tide–flood scenario.…”