The role of nutrient loading and eutrophication in estuarine ecology.

Abstract

Eutrophication is a process that can be defined as an increase in the rate of supply of organic matter (OM) to an ecosystem. We provide a general overview of the major features driving estuarine eutrophication and outline some of the consequences of that process. The main chemical constituent of OM is carbon (C), and therefore rates of eutrophication are expressed in units of C per area per unit time. OM occurs in both particulate and dissolved forms. Allochthonous OM originates outside the estuary, whereas autochthonous OM is generated within the system, mostly by primary producers or by benthic regeneration of OM. The supply rates of limiting nutrients regulate phytoplankton productivity that contributes to inputs of autochthonous OM. The trophic status of an estuary is often based on eutrophication rates and can be categorized as oligotrophic (<100 g C m(-2) y(-1), mesotrophic (100-300 g C m(-2) y(-1), eutrophic (300-500 g C m(-2) y(-1), or hypertrophic (>500 g C m(-2) y(-1). Ecosystem responses to eutrophication depend on both export rates (flushing, microbially mediated losses through respiration, and denitrification) and recycling/regeneration rates within the estuary. The mitigation of the effects of eutrophication involves the regulation of inorganic nutrient (primarily N and P) inputs into receiving waters. Appropriately scaled and parameterized nutrient and hydrologic controls are the only realistic options for controlling phytoplankton blooms, algal toxicity, and other symptoms of eutrophication in estuarine ecosystems.

Molecular insights into a dinoflagellate bloom

“…Primary productivity was also slightly higher at the bloom station compared with the annual average, although not statistically significant (Student's t-test, P-value = 0.12). Concentrations of accessory pigments were used to distinguish the presence of different phytoplankton groups (Pinckney et al, 2001;Peierls et al, 2003). Among the accessory pigments measured, peridinin and fucoxanthin were used as proxies of dinoflagellate and diatom relative abundances, respectively.…”

Impacts of Mariculture on the Diversity of Bacterial Communities within Intertidal Sediments in the Northeast of China

“…In order to achieve sustainable development, mariculture farms have moved from near-shore to off-coastal regions in recent years [30]. Mariculture in offcoastal regions is thought to have less negative environmental impacts because the strong currents reduce the environmental pollution accumulation in the regions and also benefit culture [31]. Recent molecular analyses indicated that fish farming in coastal shallow water has a greater impact on sediment bacteria than that in open water and potentially enrich both fish and human pathogens in Baltic Sea sediment [32].…”

Exposure factors for marine eutrophication impacts assessment based on a mechanistic biological model

“…Examples of these include global, estuarine, and coastal marine nitrogen cycling Herbert, 1999;Pinckney et al, 2001;Rabalais, 2002;Ryther and Dunstan, 1971;Vitousek et al, 1997), fate modelling in soils, groundwater, and surface freshwater systems Seitzinger et al, 2010Seitzinger et al, , 2005Van Drecht et al, 2003;Wollheim et al, 2008), atmospheric emissions and deposition (Lee et al, 1997;Roy et al, 2012;van Vuuren et al, 2011), emissions from agriculture (Beusen et al, 2008;Bouwman et al, 2009Bouwman et al, , 2002Butterbach-Bahl and Dannenmann, 2011;Carpenter et al, 1998), emissions from wastewater (Van Drecht et al, 2009, loadings from rivers Kroeze et al, 2012;Seitzinger et al, 2010), or impacts from excess nitrogen inputs and eutrophication to marine ecosystems (Cloern, 2001;de Jonge et al, 2002;Kitsiou and Karydis, 2011;Rabalais et al, 2009;Smith et al, 2006.…”