MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 206:87-95 (2000) - doi:10.3354/meps206087 Effect of nutrient supply on the biomass structure of planktonic communities: an experimental test on a Mediterranean coastal community Carlos M. Duarte1,*, Susana Agustí1, Josep M. Gasol2, Dolors Vaqué2, Evaristo Vazquez-Dominguez2 1Instituto Mediterráneo de Estudios Avanzados (IMEDEA), CSIC-Universitat de les Illes Balears, c/ Miguel Marqués, 21, 07190 Esporles (Mallorca), Spain 2Institut de Ciencies del Mar, CSIC, Passeig Joan de Borbó s/n, 08039 Barcelona, Spain *E-mail: cduarte@uib.es ABSTRACT: The hypothesis that increasing nutrient supply increases the biomass of autotrophs proportionately more than the biomass of heterotrophs was tested by increasing (0, 1-, 2-, 4-, 8-, and 16-fold over the background loading of 5 mmol N m-2 d-1, 1.6 mmol Si m-2 d-1, and 0.25 mmol P m-2 d-1) the addition of nutrients to large (33000 l) mesocosm units enclosing an oligotrophic coastal Mediterranean planktonic community. Autotrophic plankton biomass increased 50-fold along the range of nutrient inputs, whereas heterotrophic biomass increased only 10-fold. Heterotrophic biomass increased as the 1Ž5 power of the increase in the biomass of autotrophs, implying that the ratio of heterotroph to autotroph biomass (HB/AB ratio) declined rapidly as the biomass of autotrophs increases with increasing nutrient inputs. The biomass distribution within the community shifted from an Œinverted pyramid¹ distribution, involving greater biomass of heterotrophs than that of autotrophs, at low nutrient inputs, to the conventional Œupward¹ pyramid pattern, where the biomass of autotrophs exceeds that of consumers, at the highest nutrient inputs. This shift stabilized after 4 d, and the pyramids remained quite constant for the rest of the experiment. The experimental test presented supports the hypothesis that the relative biomass distribution between heterotrophs and autotrophs is regulated by nutrient supply. KEY WORDS: Mediterranean · Plankton · Biomass distribution · Autotrophs · Heterotrophs · Nutrient inputs · Mesocosm Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 206. Online publication date: November 03, 2000 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2000 Inter-Research.
The hypothesis that the morphometric characteristics of the littoral zone of lakes are a major determinant of submerged macrophyte biomass was tested in Lake Memphremagog (Québec‐Vermont) by studying the relationship between maximum biomass of submerged macrophytes and physical and sediment characteristics of the littoral zone. The slope of the littoral zone accounted for 72% of the observed variability in maximum submerged macrophyte biomass (MSMB). By also incorporating sediment organic matter the variance explained was raised to 88% ( P < 0.0001). A model based on only slope as predictor of MSMB was improved by considering slopes ≷5.33%: urn:x-wiley:00243590:media:lno19863151072:lno19863151072-math-0001 The power of these two equations to predict the MSMB in a variety of temperate lakes was high ( r = 0.90, P < 0.0001). However, the temperate zone model overestimates the MSMB in highly turbid lakes where irradiance rather than slope is pre‐eminent and underestimates the biomass in semitropical and tropical lakes.
The proliferation of a number of pressures affecting the ocean is leading to a growing concern that the state of the ocean is compromised, which is driving society into pessimism. Ocean calamities are disruptive changes to ocean ecosystems that have profound impacts and that are widespread or global in scope. However, scrutiny of ocean calamities to ensure that they can be confidently attributed to human drivers, operate at widespread or global scales, and cause severe disruptions of marine social-ecosystems shows that some of the problems fail to meet these requirements or that the evidence is equivocal. A number of biases internal and external to the scientific community contribute to perpetuating the perception of ocean calamities in the absence of robust evidence. An organized auditing of ocean calamities may deliver a more precise diagnosis of the status of the oceans, which may help to identify the most pressing problems that need be addressed to conserve a healthy ocean.
Net community production (NCP) is a relevant parameter informing on the role of plankton communities as sinks or sources of CO 2 in the ocean. We assessed the effect of ultraviolet (UV) radiation on NCP in different regions along the coast of Western Australia (WA). We compared 57 NCP measurements of surface communities receiving full-spectrum natural solar radiation, to communities with natural UVB radiation excluded (NCP -UV ). Very high values of incident UVB radiation were registered, especially during spring and summer (up to 75 kJ m -2 d -1 ). Although a strong inhibitory effect of UVB on NCP was expected due to the high UVB levels, no significant differences between NCP and NCP -UV were observed in any sampled region. However, we found a general trend of NCP inhibition by 33.4% under UVB radiation along the WA coast. While NCP of autotrophic communities tended to slightly decrease under UVB radiation, no robust pattern was observed for heterotrophic communities. Experiments measuring the response of NCP exposed to a gradient of enhanced UVB doses exhibited a UV dose-dependent inhibition of NCP in estuarine communities (i.e. higher inhibition with higher UVB doses), and a UV dose-independent inhibition in coastal communities. Our in situ data showed that the net metabolism of surface plankton communities from the coast of WA was insignificantly affected by elevated environmental UVB radiation levels.
Standard metabolic theory predicts that both respiration and photosynthesis should increase with increasing temperature, albeit at different rates. However, test of this prediction for ocean planktonic communities is limited, despite the broad consequences of this prediction in the present context of global ocean warming. We compiled a large data set on volumetric planktonic metabolism in the open ocean and tested the relationship between specific metabolic rates and water temperature. The relationships derived are consistent with predictions derived from metabolic theory of ecology, yielding activation energy for planktonic metabolism consistent with predictions from the metabolic theory. These relationships can be used to predict the effect of warming on ocean metabolism and, thus, the role of planktonic communities in the flow of carbon in the global ocean.
High seas fishing is described by a modular network coupled with a heterogeneous hierarchy of harbors and countries.
Last week, the United States designated nearly 140,000 square miles of the Pacific Ocean northwest of Hawaii as the largest protected marine reserve in the world. This is good news, considering that earlier this year, 4000 delegates left the international Conference of the Parties to the Convention on Biological Diversity (held in March 2006 in Brazil) with mixed feelings. Portrayal of the conference as successful by the Executive Secretary was in stark contrast to the frustration expressed by environmentalist groups about the failure to progress toward creating large marine protected areas. Paradoxically, the fact that the oceans are the patrimony of all nations creates a legislation gap that is the major obstacle to increasing the percent of protected ocean to the 10% targeted by the convention. This obstacle is augmented by a lack of awareness by legislators and the general public about the role, status, and prospects of biological diversity in oceans relative to the land. Until a better understanding of the diversity of and threats to life in the oceans is achieved, there will be no progress in protecting marine biodiversity. The vast richness of marine biodiversity remains to be discovered, particularly in remote habitats such as the deep ocean. There is a widespread misconception that extinction in the ocean is unlikely because of its huge biogeographical ranges and high connectivity of habitat. But recent surveys and molecular analyses of ocean samples have revealed marine invertebrates with biogeographical ranges as small as 4 km. Specialized communities in deep-sea habitats, such as hydrothermal vents and cold seeps, are isolated across thousands of kilometers. Marine diversity is much more extensive and vulnerable than previously thought. Moreover, much of this diversity is microbial and therefore generally unappealing to society. Indeed, more charismatic animals and plants receive most of the conservationists' attention. Scientific research must unveil the importance of ocean life diversity, test for declines in important taxa and ecosystems, elucidate the causes of these declines, and provide remedial options to change these perception biases. ![Figure][1] Although research on biodiversity has increased, these efforts are dominated by studies on land. Between 1987 and 2004, only 9.8% of published research dealt with marine biodiversity. This severe imbalance percolates through international programs. For instance, only about 10% of the First Open Science Conference of the Diversitas Programme (November 2005 in Mexico) that dealt with biodiversity science addressed marine biodiversity. This disproportionally small research effort on marine biodiversity is in sharp contrast to the large genomic diversity in the oceans as compared to that on land. Most branches of the evolutionary tree of life thrive in the oceans, whereas most terrestrial species are contained within only two branches, a result of the extended history of life in the oceans (3500 million years). The genomic richness of the ocean is an untapped resource for biotechnology, pharmacy, and food. The number of marine species brought into aquaculture exceeds, after only 30 years of development, the number of animal species domesticated over 10,000 years of husbandry on land. Realizing these opportunities requires progress to improve our present knowledge about sustainably managing marine resources. The oceans have lost much of their fish biomass and megafauna to hunting, and key coastal habitats are lost globally at rates 2 to 10 times faster than those in tropical forests [also see the Report by Lotze et al. in this issue (p. [1806][2])]. Anthropogenic inputs to the ocean are causing hypoxia and widespread deterioration of water quality, and anthropogenic CO2 emissions are causing ocean acidification, which is emerging as a global threat to calcifying marine organisms. The concept of protected areas that emerged from studies of life on land cannot be readily extrapolated to the ocean. Until last week, the total protected marine area was 10 times smaller than that on land, and most marine protected areas are too small to be effective. Mounting evidence indicates that marine food webs are connected across oceanic scales, but the forces driving these connections are poorly understood. We must improve our understanding of how the global ocean ecosystem works in order to design networks of protected areas that effectively preserve biodiversity. Indeed, as Mora et al. point out in this issue (p. [1750][3]), the present design of some marine protected areas may not be optimal. Further promoting marine biodiversity research requires a larger scientific community and more resources than currently exist. This can be achieved through increased international cooperative efforts and networking. We must do this before we face a future depleted of marine resources. [1]: pending:yes [2]: /lookup/doi/10.1126/science.1128035 [3]: /lookup/doi/10.1126/science.1125295
Domestication has had higher success rates in the sea relative to those seen in the long history of land species' domestication. The rise of aquaculture has global consequences.
