Threats to Ultraoligotrophic Marine Ecosystems

Kletou, Demetris; Hall‐Spencer, Jason M.

doi:10.5772/34842

Cited by 18 publications

(15 citation statements)

References 213 publications

(209 reference statements)

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“…Our findings contrast with several studies of oceanic species which reported significant, positive interactions of elevated CO2 on cyanobacterial photosynthesis, nitrogen fixation and growth [87][88][89]. These experiments appear to have been conducted in nutrient replete conditions; in oligotrophic conditions, such as off Sicily and in mid-ocean gyres, cyanobacteria may not respond positivity to levels of CO2 enrichment predicted this century [90].…”

Section: Discussioncontrasting

confidence: 99%

Marine Microphytobenthic Assemblage Shift along a Natural Shallow-Water CO2 Gradient Subjected to Multiple Environmental Stressors

Johnson

Brownlee

Milazzo

et al. 2015

JMSE

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Predicting the effects of anthropogenic CO2 emissions on coastal ecosystems requires an understanding of the responses of algae, since these are a vital functional component of shallow-water habitats. We investigated microphytobenthic assemblages on rock and sandy habitats along a shallow subtidal pCO2 gradient near volcanic seeps in the Mediterranean Sea. Field studies of natural pCO2 gradients help us understand the likely effects of ocean acidification because entire communities are subjected to a realistic suite of environmental stressors such as over-fishing and coastal pollution. Temperature, total alkalinity, salinity, light levels and sediment properties were similar at our study sites. On sand and on rock, benthic diatom abundance and the photosynthetic standing crop of biofilms increased significantly with increasing pCO2. There were also marked shifts in diatom community composition as pCO2 levels increased. Cyanobacterial abundance was only elevated at extremely high levels of pCO2 (>1400 μatm). This is the first demonstration of the tolerance of natural marine benthic microalgae assemblages to elevated CO2 in an ecosystem subjected to multiple environmental stressors. Our observations indicate that

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Section: Discussioncontrasting

confidence: 99%

Marine Microphytobenthic Assemblage Shift along a Natural Shallow-Water CO2 Gradient Subjected to Multiple Environmental Stressors

Johnson

Brownlee

Milazzo

et al. 2015

JMSE

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“…Such low nutrient concentrations are typically found in oligotrophic waters and are expected to constrain phytoplankton growth. Yet chlorophyll a (Chl a ) concentrations, a proxy for phytoplankton biomass, were relatively high in both lagoons, with values ≥ 0.8 µg l −1 , in the range typically found in meso‐ to eutrophic marine environments (Kletou and Hall‐Spencer, ). Chlorophyll a concentrations were lower in Nirasa (0.798–1.666 µg l −1 ) than in New Georgia (1.255–2.221 µg l −1 ).…”

Section: Resultsmentioning

confidence: 99%

Oligotrophic lagoons of the South Pacific Ocean are home to a surprising number of novel eukaryotic microorganisms

Kim

Sprung

Duhamel

et al. 2016

Environmental Microbiology

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The diversity of microbial eukaryotes was surveyed by environmental sequencing from tropical lagoon sites of the South Pacific, collected through the American Museum of Natural History (AMNH)'s Explore21 expedition to the Solomon Islands in September 2013. The sampled lagoons presented low nutrient concentrations typical of oligotrophic waters, but contained levels of chlorophyll a, a proxy for phytoplankton biomass, characteristic of meso- to eutrophic waters. Two 18S rDNA hypervariable sites, the V4 and V8-V9 regions, were amplified from the total of eight lagoon samples and sequenced on the MiSeq system. After assembly, clustering at 97% similarity, and removal of singletons and chimeras, a total of 2741 (V4) and 2606 (V8-V9) operational taxonomic units (OTUs) were identified. Taxonomic annotation of these reads, including phylogeny, was based on a combination of automated pipeline and manual inspection. About 18.4% (V4) and 13.8% (V8-V9) of the OTUs could not be assigned to any of the known eukaryotic groups. Of these, we focused on OTUs that were not divergent and possessed multiple sources of evidence for their existence. Phylogenetic analyses of these sequences revealed more than ten branches that might represent new deeply-branching lineages of microbial eukaryotes, currently without any cultured representatives or morphological information.

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“…Also, our findings revealed that a direct effect of ocean acidification on the vital rates of copepods was not obvious. However, the combination of low pH with the ambient oligotrophic conditions (Chl α <1 μg l -1 , Shushkina et al, 1997), where organisms were more vulnerable due to lack of food, and warming which affect physiological rates at the individual level perhaps reduces the ability of the species to allocate resources for coping with multiple stressors (Kletou & Hall-Spencer, 2012). In this respect, the effect of ocean acidification in the oligotrophic environment of the Mediterranean Sea could be more profound, altering the overall plankton community structure.…”

Section: Discussionmentioning

confidence: 99%

Effects of low pH and raised temperature on egg production, hatching and metabolic rates of a Mediterranean copepod species (Acartia clausi) under oligotrophic conditions

et al. 2013

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. Effects of low pH and raised temperature on egg production, hatching and metabolic rates of a Mediterranean copepod species (Acartia clausi) under oligotrophic conditions. Mediterranean Marine Science, 15(1) Mar. Sci., 15/1, 2014, 74-83 Effects of low pH and raised temperature on egg production, hatching and metabolic rates of a Mediterranean copepod species (Acartia clausi) under oligotrophic conditions AbstractThis study includes the first information on the combined effect of low pH and raised temperature on egg production rate (EP), hatching success (HS), excretion and respiration of the Mediterranean copepod Acartia clausi. Adult individuals of A. clausi and fresh surface seawater were collected at a coastal station in Saronikos Gulf during April 2012. Four different conditions were applied: two different pH levels (present: 8.09 and future: 7.83) and two temperature values (present: 16°C and present+4°C= 20°C). EP and HS decreased significantly over the duration of exposure at future pH under both temperature conditions. However, the analysis of the combined effect of pH, T, chlorophyll α and the duration of the EP and HS experiments revealed that ocean acidification had no discernible effect, whereas warming, food and the duration of exposure were more significant for the reproductive output of A. clausi. Temperature appeared to have a positive effect on respiration and excretion. Acidification had no clear effect on respiration, but a negative effect on excretion was observed. Acidification and warming resulted in an increase of the excretion rate and the increase was higher than that observed by warming only. Our findings show that acidification does not have an obvious direct effect on the vital rates of the copepod, with the exception of excretion possibly. Therefore, the combination of acidification, ambient oligotrophic conditions and warming could affect the ability of the species to allocate resources for coping with multiple stressors.

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Threats to Ultraoligotrophic Marine Ecosystems

Cited by 18 publications

References 213 publications

Marine Microphytobenthic Assemblage Shift along a Natural Shallow-Water CO2 Gradient Subjected to Multiple Environmental Stressors

Marine Microphytobenthic Assemblage Shift along a Natural Shallow-Water CO2 Gradient Subjected to Multiple Environmental Stressors

Oligotrophic lagoons of the South Pacific Ocean are home to a surprising number of novel eukaryotic microorganisms

Effects of low pH and raised temperature on egg production, hatching and metabolic rates of a Mediterranean copepod species (Acartia clausi) under oligotrophic conditions

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