Nutrient limitation and the eutrophication of coastal lagoons

Abstract

An ecosystem-level experiment was conducted to identify the nutrient most limiting to productivity and biomass in the marine lagoons of the northeast United States. Mesocosms containing a complex of species characteristic of shallow coastal marine environments were enriched with P alone, N alone, or combined N plus P, at loadings typical of highly enriched natural lagoons. The mesocosms showed significant responses to ennchment with N alone but not P alone, indicating limitation by N. Enrichment with N alone caused increased water column concentrations of chlorophyll a and particulate nitrogen [PN), increased water column daytime net production (NP), and increased rates of growth of juvenile winter flounder. It also caused eelgrass beds and mats of drift macroalgae to decline, apparently in response to phytoplankton shading. Comparison of the N-alone and combined N + P treatments indicated that when enriched with N alone, the limitation of the systems shifted to P limitation of total system metabolism and of phytoplankton production and standing crop, and to light limitation of eelgrass and macroalgal growth. In the combined N + P mesocosms, water column concentrations of chlorophyll a, PN, and particulate P, rates of total system and water column NP and night-time respiration, and growth rates of juvenile winter flounder and killlfish were all increased relative to the N-alone mesocosms. Declines of eelgrass and macroalgae were also more severe.

The meiofaunal community structure of a Mediterranean lagoon (Gialova lagoon, Ionian Sea)

“…Research has shown that nutrient limitation in lagoons is a complex matter; in particular nitrogen limitation is important (Nixon 1982;Taylor et al 1995). During the summer and spring, raw nutrients are more important in Gialova, reflecting the growth stage of meiofaunal food (bacteria, microphytoplankton) and perhaps limiting distribution and density.…”

The response of primary producer assemblages to mitigation measures to reduce eutrophication in a temperate estuary

“…Some systems have shown a phytoplankton dominated-response (Taylor et al, 1995) while others presented macroalgal dominance (Lavery and McComb, 1991;Valiela et al, 1992). Shallow coastal estuaries with low nutrient availability in the water are more likely to be dominated by benthic algae and vascular plants due to the potential of these species to sequester nutrients from the sediments (Sand-Jensen and Borum, 1991;Havens et al, 2001).…”

“…In estuarine systems, plant communities are constituted by complex assemblages of phytobenthos and phytoplankton, each with different access to nutrients and light (Taylor et al, 1995) that can constitute potentially limiting factors to the primary production of these aquatic autotrophs (Pedersen and Borum, 1992). Phytoplankton and fast-growing ephemeral macroalgae are often limited by nutrient availability, while slow-growing perennial macroalgae and rooted macrophytes seem less dependent on nutrient concentrations (Sand-Jensen and Borum, 1991).…”

Macroalgal blooms in shallow estuaries: Controls and ecophysiological and ecosystem consequences

“…Duarte (I 995), Taylor et al (1995), and others have suggested that in waters where nutrient supply increases, seagrasses are replaced by macroalgae, which in turn can be replaced by phytoplankton as the dominant producers. Here we use data from different estuaries of Waqlloit Bay to put together a quantitative de- piction of how seagrasses might be replaced by macroalgae and phytoplankton as the dominant producers, under the influence of progressive nitrogen enrichment (Fig.…”