TY - JOUR

T1 - In situ and experimental evidence for effects of elevated pH on protistan and metazoan grazers

AU - Hansen, Benni W.

AU - Andersen, Christian M. B.

AU - Hansen, Per Juel

AU - Nielsen, Torkel G.

AU - Vismann, Bent

AU - Tiselius, Peter

PY - 2019

Y1 - 2019

N2 - Plankton succession was studied in a hyper-eutrophic stratified estuary, Mariager Fjord, Denmark. Above the pycnocline (15 m) pH increased from 8.5 to 9.2 after 5 d of sunny weather due to high primary production. The protistan grazers were dominated by heterotrophic dinoflagellates and mixotrophic and heterotrophic ciliates. Metazooplankton was dominated by meroplankton, rotifers, and the copepod, Acartia tonsa, all with a relatively low biomass. Cirriped nauplii occupied the upper strata while polychaete larvae the whole water column. Bivalve larvae occurred occasionally above the pycnocline even at very high pH. In exposure experiments the mixotrophic ciliate Mesodinium rubrum was the least pH tolerant species, followed by Strombidium spp., which did not cope well with seawater pH >8.5. Some heterotrophic dinoflagellates were more tolerant with net growth at pH >9. The predominant rotifer Synchaeta sp. tolerated up to pH 9.5 and the copepod survived pH 10 but stopped producing eggs at pH 9.5 with unaffected egg hatching success. The polychaeta and cirripedia larvae tolerated pH 9.5, but bivalvia larvae showed decreased survival already at pH 8.5. Based on in situ distribution patterns and pH exposure experiments we suggest that pH indeed contribute to structuring zooplankton distribution.

AB - Plankton succession was studied in a hyper-eutrophic stratified estuary, Mariager Fjord, Denmark. Above the pycnocline (15 m) pH increased from 8.5 to 9.2 after 5 d of sunny weather due to high primary production. The protistan grazers were dominated by heterotrophic dinoflagellates and mixotrophic and heterotrophic ciliates. Metazooplankton was dominated by meroplankton, rotifers, and the copepod, Acartia tonsa, all with a relatively low biomass. Cirriped nauplii occupied the upper strata while polychaete larvae the whole water column. Bivalve larvae occurred occasionally above the pycnocline even at very high pH. In exposure experiments the mixotrophic ciliate Mesodinium rubrum was the least pH tolerant species, followed by Strombidium spp., which did not cope well with seawater pH >8.5. Some heterotrophic dinoflagellates were more tolerant with net growth at pH >9. The predominant rotifer Synchaeta sp. tolerated up to pH 9.5 and the copepod survived pH 10 but stopped producing eggs at pH 9.5 with unaffected egg hatching success. The polychaeta and cirripedia larvae tolerated pH 9.5, but bivalvia larvae showed decreased survival already at pH 8.5. Based on in situ distribution patterns and pH exposure experiments we suggest that pH indeed contribute to structuring zooplankton distribution.

U2 - 10.1093/plankt/fbz020

DO - 10.1093/plankt/fbz020

M3 - Journal article

VL - 41

SP - 257

EP - 271

JO - Journal of Plankton Research

JF - Journal of Plankton Research

SN - 0142-7873

IS - 3

ER -