Distributions of virio- and picoplankton and their relationships with ice-melting and upwelling in the Indian Ocean sector of East Antarctica
Meiaoxue HanShunan CaoGuangfu LuoJianfeng HeYantao LiangXuechao ChenChengxiang GuGang LiuZiyue WangWenjing ZhangYue DongJun ZhaoQiang HaoHongbing ShaoYeong Yik SungWen Jye MokLi Lian WongAndrew McMinnMin Wang
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Coastal upwelling occurs under the combined effect of wind stress and Earth's rotation. The nutrients carried up by upwelling have great impact on primary production and fisheries. For using autonomous underwater vehicles (AUVs) to investigate complex coastal upwelling ecosystems, we have developed algorithms for an AUV to autonomously distinguish between upwelling and stratified water columns based on the vertical temperature difference between shallow and deep depths, and to accurately detect an upwelling front based on the horizontal gradient of the vertical temperature difference in the water column. During a June 2011 experiment in Monterey Bay, California, the Dorado AUV flew on a transect from an upwelling shadow region (stratified water column), through an upwelling front, and into an upwelling water column. Running our algorithms, the AUV successfully classified the three distinct water types, accurately located the narrow front, and acquired targeted water samples from the three water types. Molecular analysis of the AUV‐acquired water samples shows that mussels, calanoid copepods, and podoplean copepods were most abundant in the upwelling shadow region and nonexistent in the upwelling water column. Calanoid copepods were moderately abundant in the water samples collected from the upwelling front. These results are largely consistent with previous findings from zooplankton population surveys conducted with the Dorado AUV in Monterey Bay in 2009. The novel detecting and targeted sampling capabilities permit an AUV to autonomously conduct “surgical sampling” of a complex marine ecosystem.
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We assessed relationships between phytoplankton standing stock, measured as chlorophyll a (Chl a ), primary production (PP), and heterotrophic picoplankton production (HPP), in the epipelagic zone (0–100 m) as well as in the mesopelagic zone (100–1,000 m) in the polar frontal zone of the Atlantic sector of the Southern Ocean in austral summer (late December to January) and fall (March to early May). Integrated epipelagic HPP was positively correlated to integrated PP in summer (data for fall are not available) but not to integrated Chl a . However, integrated mesopelagic HPP was positively correlated to Chl a in summer as well as fall. The mesopelagic fraction of HPP as a percentage of total HPP was also positively correlated to Chl a , whereas the epipelagic fraction of HPP was negatively correlated to it. These results indicate that with increasing phytoplankton standing stock, constituted mainly of highly silicified diatoms, the focus of its consumption by heterotrophic picoplankton shifts from epipelagic to mesopelagic waters. With a growth efficiency of 30%, our HPP data indicate that in both the epipelagic and mesopelagic zone heterotrophic picoplankton consume 20% of PP. Mesopelagic heterotrophic picoplankton consumed around 80% of the sinking flux, measured from depletion of 234 Th, which is a lower fraction than that reported from the central and subarctic Pacific. Our analysis indicates that it is important to include mesopelagic HPP in comprehensive assessments of the microbial consumption of PP, phytoplankton biomass, and particulate organic matter in cold oceanic systems with high rates of export production.
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Summary Members of the prokaryotic picoplankton are the main drivers of the biogeochemical cycles over large areas of the world's oceans. In order to ascertain changes in picoplankton composition in the euphotic and twilight zones at an ocean basin scale we determined the distribution of 11 marine bacterial and archaeal phyla in three different water layers along a transect across the Atlantic Ocean from South Africa (32.9°S) to the UK (46.4°N) during boreal spring. Depth profiles down to 500 m at 65 stations were analysed by catalysed reporter deposition fluorescence in situ hybridization (CARD‐FISH) and automated epifluorescence microscopy. There was no obvious overall difference in microbial community composition between the surface water layer and the deep chlorophyll maximum (DCM) layer. There were, however, significant differences between the two photic water layers and the mesopelagic zone. SAR11 (35 ± 9%) and Prochlorococcus (12 ± 8%) together dominated the surface waters, whereas SAR11 and Crenarchaeota of the marine group I formed equal proportions of the picoplankton community below the DCM (both ∼15%). However, due to their small cell sizes Crenarchaeota contributed distinctly less to total microbial biomass than SAR11 in this mesopelagic water layer. Bacteria from the uncultured Chloroflexi ‐related clade SAR202 occurred preferentially below the DCM (4–6%). Distinct latitudinal distribution patterns were found both in the photic zone and in the mesopelagic waters: in the photic zone, SAR11 was more abundant in the Northern Atlantic Ocean (up to 45%) than in the Southern Atlantic gyre (∼25%), the biomass of Prochlorococcus peaked in the tropical Atlantic Ocean, and Bacteroidetes and Gammaproteobacteria bloomed in the nutrient‐rich northern temperate waters and in the Benguela upwelling. In mesopelagic waters, higher proportions of SAR202 were present in both central gyre regions, whereas Crenarchaeota were clearly more abundant in the upwelling regions and in higher latitudes. Other phylogenetic groups such as the Planctomycetes , marine group II Euryarchaeota and the uncultured clades SAR406, SAR324 and SAR86 rarely exceeded more than 5% of relative abundance.
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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 412:11-27 (2010) - DOI: https://doi.org/10.3354/meps08648 Autotrophic picoplankton in mesozooplankton guts: evidence of aggregate feeding in the mesopelagic zone and export of small phytoplankton S. E. Wilson1,*, D. K. Steinberg2 1Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, California 95039, USA 2Virginia Institute of Marine Science, College of William and Mary, Route 1208 Greate Road, Gloucester Point, Virginia 23062, USA *Email: sewilson@mbari.org ABSTRACT: Zooplankton play a key role in affecting the efficiency by which organic matter is exported to depth. Mesozooplankton consumption of detrital aggregates has been hypothesized as a mechanism for enhancing the export of picoplankton from surface layers. We analyzed the gut contents of mesopelagic copepods and ostracods using light and epifluorescence microscopy to determine if cyanobacteria and eukaryotic phytoplankton too small to be ingested individually were present. Hind-guts were dissected from multiple species collected in discrete depth intervals between 0 and 1000 m during the day and night, at contrasting sites in the subtropical (Hawaii Ocean Time-series site ALOHA) and subarctic (Japanese time-series site K2) Pacific Ocean. Autofluorescing cyanobacteria and small eukaryotic phytoplankton were found in the guts of nearly all species sampled from all depths, indicating consumption of aggregates. Some of the cyanobacteria and other small cells ingested may have originated from inside the guts, or as symbionts, of microzooplankton, which were also common in the guts of many of these species. At both sites, most species' guts contained higher concentrations of cyanobacteria and small phytoplankton at night than during the day. Ostracod guts at ALOHA contained higher densities of picoplankton than those at K2, reflecting the predominance of smaller cells at ALOHA. Guts of diel vertical migrators still contained picoplankton at their deep, daytime residence depths, indicating active export of these cells. Our results indicate mesozooplankton grazing on aggregates is a pathway by which flux of picoplankton can be enhanced. KEY WORDS: Zooplankton · Gut contents · Cyanobacteria · Picoplankton · Marine snow · Biological pump · Mesopelagic zone · Diel vertical migration Full text in pdf format PreviousNextCite this article as: Wilson SE, Steinberg DK (2010) Autotrophic picoplankton in mesozooplankton guts: evidence of aggregate feeding in the mesopelagic zone and export of small phytoplankton. Mar Ecol Prog Ser 412:11-27. https://doi.org/10.3354/meps08648 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 412. Online publication date: August 18, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.
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Mesopelagic zone
Bathyal zone
Deepwater Horizon
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Abstract Is there a mesopelagic protist fauna composed of species different from that of the overlying surface community? Does the mesopelagic community show seasonal changes in abundances and species composition? We addressed these questions by considering three distinct groups in which species identification is relatively unambiguous: tintinnid ciliates, phaeodarian radiolarians, and amphisolenid dinoflagellates. We sampled weekly at 250 m and 30 m depth from January to June a deep-water coastal site characterized by seasonal changes in water column structure; notably, in winter the mixed layer extends down into mesopelagic depths. We found a deep-water community of tintinnid ciliates comprised of forms apparently restricted to deep waters and species also found in the surface layer. This latter group was dominant during the winter mixis period when tintinnid concentrations were highest and subsequently declined with water column stratification. Phaeodarian radiolarians and the amphisolenid dinoflagellates were regularly found in deep samples but were largely absent from surface water samples and showed distinct patterns in the mesopelagic. Phaeodarian radiolarians declined with water column mixing and then increased in concentration with water column stratification whilst amphisolenid dinoflagellates concentrations showed no pattern but species composition varied. We conclude that for all three protists groups there appear to be both distinct mesopelagic forms and seasonal patterns.
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Stratification (seeds)
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The pelagic environment can be divided into five gross regions. These are the intertidal and estuarine, the neritic and the oceanic epipelagic, mesopelagic and bathypelagic regions. Each of these regions has an endemic crustacean fauna but many species inhabit more than one region. The ranges and rates of fluctuations of environmental characteristics vary from the extremes encountered in the intertidal and estuarine region to the relative constancy of those in the bathypelagic region.
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Fear of predation can have wide-ranging ecological effects.1Brown J.S. Laundré J.W. Gurung M. The ecology of fear: optimal foraging, game theory, and trophic interactions.J. Mammal. 1999; 80: 385-399Crossref Scopus (763) Google Scholar, 2Creel S. Christianson D. Relationships between direct predation and risk effects.Trends Ecol. Evol. 2008; 23: 194-201Abstract Full Text Full Text PDF PubMed Scopus (671) Google Scholar, 3Laundré J.W. Hernández L. Ripple W.J. The landscape of fear: ecological implications of being afraid.Open Ecol. J. 2010; 3: 1-7Crossref Scopus (409) Google Scholar, 4Ripple W.J. Beschta R.L. Wolves and the ecology of fear: can predation risk structure ecosystems?.Bioscience. 2004; 54: 755-766Crossref Scopus (464) Google Scholar This is especially true in the ocean's pelagic zone, the Earth's largest habitat, where vertical gradients in light and primary productivity force numerous taxa to migrate vertically each night to feed at the surface while minimizing risk from visual predators.5Longhurst A.R. Vertical migration.in: Cushing E.D. Walsh J.J. The Ecology of the Seas. W.B. Saunders Company, 1976: 116-137Google Scholar, 6Aksnes D.L. Utne A.C.W. A revised model of visual range in fish.Sarsia. 1997; 82: 137-147Crossref Scopus (154) Google Scholar, 7Hays G.C. A review of the adaptive significance and ecosystem consequences of zooplankton diel vertical migrations.Hydrobiologia. 2003; 503: 163-170Crossref Scopus (509) Google Scholar Despite its importance and the fact that it is driven by spatial differences in perceived risk,8Gaynor K.M. Brown J.S. Middleton A.D. Power M.E. Brashares J.S. Landscapes of fear: spatial patterns of risk perception and response.Trends Ecol. Evol. 2019; 34: 355-368Abstract Full Text Full Text PDF PubMed Scopus (162) Google Scholar diel vertical migration (DVM) is rarely considered within the "landscape of fear"3Laundré J.W. Hernández L. Ripple W.J. The landscape of fear: ecological implications of being afraid.Open Ecol. J. 2010; 3: 1-7Crossref Scopus (409) Google Scholar,8Gaynor K.M. Brown J.S. Middleton A.D. Power M.E. Brashares J.S. Landscapes of fear: spatial patterns of risk perception and response.Trends Ecol. Evol. 2019; 34: 355-368Abstract Full Text Full Text PDF PubMed Scopus (162) Google Scholar,9Bleicher S.S. The landscape of fear conceptual framework: definition and review of current applications and misuses.PeerJ. 2017; 5: e3772Crossref PubMed Scopus (61) Google Scholar framework.10Beltran R.S. Kendall-Bar J.M. Pirotta E. Adachi T. Naito Y. Takahashi A. Cremers J. Robinson P.W. Crocker D.E. Costa D.P. Lightscapes of fear: how mesopredators balance starvation and predation in the open ocean.Sci. Adv. 2021; 7: eabd9818Crossref PubMed Scopus (14) Google Scholar It is also far from the only such process in the pelagic zone. We used continuous, year-long records from an upward-looking echosounder and broadband hydrophone at a cabled observatory off Central California, USA, to observe avoidance reactions by several groups of pelagic animals to the presence of their predators. As expected, vertical migration was ubiquitous, but we also observed behaviors at shorter and longer timescales that were best explained by fear of predation. The presence of foraging odontocetes induced immediate diving behavior in mesopelagic sound-scattering layers, and schools of epipelagic fishes induced similar reaction in layers of zooplankton and mesopelagic micronekton. At longer timescales, the presence of fish schools significantly deepened vertical migration, rearranging life throughout the water column. We argue that behavioral reactions to predation risk are common in the pelagic zone at a range of spatiotemporal scales and that our understanding of food webs and biogeochemical cycling in this immense biome will be incomplete unless we account for fear.
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Coastal upwelling zone hosts most fishing grounds worldwide and nitrogen dynamics in those systems mainly have been addressed through the nutrients replenished the ecosystem. Compared with coastal and upper-layer ecosystems, relatively limited knowledge has been explored by nitrogen isotope imprints through the food webs of mesopelagic fishes and their links to upwelling characteristics. Here, we collected several species of mesopelagic fishes in the mid-west region of the South China Sea (SCS) and analyzed them by biochemical methods (fatty acids, δ13C, δ15N, and δ13C of fatty acids). Due to the occurrence of upwelling, we want to evaluate the variation of nitrogen isotope compositions among these mesopelagic species and their links to the upwelling nitrogen supply. The δ15N of mesopelagic fishes in the non-upwelling area was depleted by 2‰ when compared with those in upwelling area, which indicated different nitrogen sources impacting for fishes in the two areas. A combination of multi-biochemical proxies was used to divide mesopelagic fishes into six groups and indicated that the feeding behaviors and upwelling were the main factors to affect the biological composition of mesopelagic fishes, even in such small regions. The differences in δ15N values between the upwelling and non-upwelling areas allowed us to estimate that N2 fixation supported about 37% of the N-demand of food sources in the non-upwelling area, which was larger than the 10% in the upwelling area. These results illustrate that nutrients from the deep layers in upwelling systems might be the main factors that cause differences in δ15N in mesopelagic fishes between upwelling and non-upwelling areas. Thus, more studies of N dynamics in mesopelagic fishes should be conducted in the upwelling systems to illustrate the impact of climate changes on fish biomass in the future.
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Mesopelagic zone
Swordfish
Bathyal zone
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