Influence of cyclonic and anticyclonic eddies on plankton in the southeastern Mediterranean Sea during late summertime
<p>Planktonic food webs were studied contemporaneously in a mesoscale cyclonic (upwelling, <span class="inline-formula">∼</span> 13 months old) and an anticyclonic (downwelling, <span class="inline-formula">∼</span> 2 months old) eddy as well as in a...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-05-01
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| Series: | Ocean Science |
| Online Access: | https://os.copernicus.org/articles/18/693/2022/os-18-693-2022.pdf |
| Summary: | <p>Planktonic food webs were studied contemporaneously in a mesoscale cyclonic (upwelling, <span class="inline-formula">∼</span> 13 months old) and an anticyclonic (downwelling,
<span class="inline-formula">∼</span> 2 months old) eddy as well as in an uninfluenced background situation in the oligotrophic southeastern Mediterranean Sea (SEMS) during
late summer 2018. We show that integrated nutrient concentrations were higher in the cyclone compared to the anticyclone or the background
stations by 2–13-fold. Concurrently, <i>Synechococcus</i> and <i>Prochlorococcus</i> were the dominant autotrophs abundance-wise in the
oligotrophic anticyclone (<span class="inline-formula">∼</span> 300 <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>10</sup></span> <span class="inline-formula">cells m<sup>−2</sup></span>). In the cyclone, functional groups such as dinoflagellates,
Prymnesiophyceae and Ochrophyta contributed substantially to the total phytoplankton abundance (<span class="inline-formula">∼</span> 14 <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>10</sup></span> <span class="inline-formula">cells m<sup>−2</sup></span>), which was <span class="inline-formula">∼</span> 65 % lower at the anticyclone and background stations (<span class="inline-formula">∼</span> 5 <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>10</sup></span> <span class="inline-formula">cells m<sup>−2</sup></span>). Primary production
was highest in the cyclonic eddy (191 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">mg</mi><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">C</mi><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">m</mi><mrow><mo>-</mo><mn mathvariant="normal">2</mn></mrow></msup><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">d</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="65pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="f333bf6796381317fdd7bb4d5d123ce7"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="os-18-693-2022-ie00001.svg" width="65pt" height="15pt" src="os-18-693-2022-ie00001.png"/></svg:svg></span></span>) and 2–5-fold lower outside the eddy area. Heterotrophic prokaryotic
cell-specific activity was highest in the cyclone (<span class="inline-formula">∼</span> 10 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">fg</mi><mspace linebreak="nobreak" width="0.125em"/><mi mathvariant="normal">C</mi><mspace width="0.25em" linebreak="nobreak"/><msup><mi mathvariant="normal">cell</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">d</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="68pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="d30002d73add2848d591ee9b7f4a1972"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="os-18-693-2022-ie00002.svg" width="68pt" height="15pt" src="os-18-693-2022-ie00002.png"/></svg:svg></span></span>), while the least productive cells were found in the
anticyclone (4 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M19" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">fg</mi><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">C</mi><mspace width="0.25em" linebreak="nobreak"/><msup><mi mathvariant="normal">cell</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">d</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="68pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="088878cf67c9ea9ae6633ee1d38407b2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="os-18-693-2022-ie00003.svg" width="68pt" height="15pt" src="os-18-693-2022-ie00003.png"/></svg:svg></span></span>). Total zooplankton biomass in the upper 300 <span class="inline-formula">m</span> was 10-fold higher in the cyclone compared
with the anticyclone or background stations (1337 vs. 112–133 <span class="inline-formula">mg C m<sup>−2</sup></span>, respectively). Copepod diversity was much higher in the
cyclone (44 species), compared to the anticyclone (6 small-size species). Our results highlight that cyclonic and anticyclonic eddies show
significantly different community structure and food-web dynamics in oligotrophic environments, with cyclones representing productive oases in the
marine desert of the SEMS.</p> |
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| ISSN: | 1812-0784 1812-0792 |