Nitrogen cycling in coastal marine ecosystems

Abstract

It is generally considered that nitrogen availability is one of the major factors regulating primary production in temperate coastal marine environments. Coastal regions often receive large anthropogenic inputs of nitrogen that cause eutrophication. The impact of these nitrogen additions has a profound effect in estuaries and coastal lagoons where water exchange is limited. Such increased nutrient loading promotes the growth of phytoplankton and fast growing pelagic macroalgae while rooted plants (sea-grasses) and benthic are suppressed due to reduced light availability. This shift from benthic to pelagic primary production introduces large diurnal variations in oxygen concentrations in the water column. In addition oxygen consumption in the surface sediments increases due to the deposition of readily degradable biomass. In this review the physico-chemical and biological factors regulating nitrogen cycling in coastal marine ecosystems are considered in relation to developing effective management programmes to rehabilitate seagrass communities in lagoons currently dominated by pelagic macroalgae and/or cyanobacteria.

Seasonal variability of denitrification efficiency in northern salt marshes: An example from the St. Lawrence Estuary

“…A large body of information is available on factors influencing denitrification in coastal marine environments (see review by Herbert, 1999). The three main factors influencing benthic denitrification are temperature, supplies of NO 3 -and availability of organic carbon (Smith et al, 1985;Yoon and Benner, 1992;Tuominen et al, 1998).…”

Coupling of carbon, nitrogen and oxygen cycles in sediments from a Mediterranean lagoon: a seasonal perspective

“…Several factors are known to influence nitrogen and oxygen dynamics, such as temperature, bottom water oxygenation, oxic zone thickness and organic matter (d, m, r) at Stns C4 and C5. In situ nitrification and denitrification rates assessed using the acetylene-blockage method; diffusive oxygen fluxes calculated from in situ microprofiles input (Henriksen & Kemp 1988, Herbert 1999, Kemp & Dodds 2002. In this system, temperature was found to be one of the main variables regulating the seasonal oxygen dynamics ).…”

In situ soft sediment nutrient enrichment: A unified approach to eutrophication field experiments

“…Indeed, excessive nutrient loading and eutrophication are stressing coastal marine environments throughout the world (Levin et al, 2015). The overabundance of nitrogen in particular the (nutrient usually limiting production (Herbert, 1999;Howarth and Marino, 2006)) causes changes in biomass, structure, and functioning of coastal communities and food webs (Abreu et al, 2006;Howarth et al, 2011;Rabalais et al, 2014). Yet, despite being of paramount importance to global environmental wellbeing, nutrient processing in soft sediments is still poorly understood and response to perturbations are rarely tested experimentally in situ.…”