Predicting marine phytoplankton community size structure from empirical relationships with remotely sensed variables
TL;DR: In this article, the authors describe relationships between the environment and the size composition of phytoplankton communities, using a collation of empirical measurements of size composition from sites that include polar, tropical and upwelling environments.
Abstract: The size composition of primary producers has a potential influence on the length of marine food chains and carbon sinking rates, thus on the proportion of primary production (PP) that is removed from the upper layers and available to higher trophic levels. While total rates of PP are widely reported, it is also necessary to account for the size composition of primary producers when developing food web models that predict consumer biomass and production. Empirical measurement of size composition over large space and time scales is not feasible, so one approach is to predict size composition from environmental variables that are measured and reported on relevant scales. Here, we describe relationships between the environment and the size composition of phytoplankton communities, using a collation of empirical measurements of size composition from sites that include polar, tropical and upwelling environments. The size composition of the phytoplankton communities can be predicted using two remotely sensed variables, chlorophyll-a concentration and sea surface temperature. Applying such relationships in combination allows prediction of the slope and location of phytoplankton size spectra and estimation of the percentage of different sized phytoplankton groups in communities.
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Inter-American Tropical Tuna Commission1, Commonwealth Scientific and Industrial Research Organisation2, Hobart Corporation3, Secretariat of the Pacific Community4, University of Massachusetts Amherst5, University of North Carolina at Wilmington6, Joint Institute for Marine and Atmospheric Research7, Monterey Bay Aquarium Research Institute8, Instituto Politécnico Nacional9, Institut de recherche pour le développement10, Aix-Marseille University11
TL;DR: Analysis of over 14,000 tuna stomachs revealed for the first time the global expanse of pelagic predatory fish diet and global patterns of micronekton diversity, suggesting the ongoing expansion of warmer, less productive waters in the world’s oceans may alter foraging opportunities for tunas due to regional changes in prey abundances and compositions.
Abstract: Predator-prey interactions for three commercially valuable tuna species: yellowfin (Thunnus albacares), bigeye (T. obesus), and albacore (T. alalunga), collected over a 40-year period from the Pacific, Indian, and Atlantic Oceans, were used to quantitatively assess broad, macro-scale trophic patterns in pelagic ecosystems. Analysis of over 14,000 tuna stomachs, using a modified classification tree approach, revealed for the first time the global expanse of pelagic predatory fish diet and global patterns of micronekton diversity. Ommastrephid squids were consistently one of the top prey groups by weight across all tuna species and in most ocean bodies. Interspecific differences in prey were apparent, with epipelagic scombrid and mesopelagic paralepidid fishes globally important for yellowfin and bigeye tunas, respectively, while vertically-migrating euphausiid crustaceans were important for albacore tuna in the Atlantic and Pacific Oceans. Diet diversity showed global and regional patterns among tuna species. In the central and western Pacific Ocean, characterized by low productivity, a high diversity of micronekton prey was detected while low prey diversity was evident in highly productive coastal waters where upwelling occurs. Spatial patterns of diet diversity were most variable in yellowfin and bigeye tunas while a latitudinal diversity gradient was observed with lower diversity in temperate regions for albacore tuna. Sea-surface temperature was a reasonable predictor of the diets of yellowfin and bigeye tunas, whereas chlorophyll-a was the best environmental predictor of albacore diet. These results suggest that the ongoing expansion of warmer, less productive waters in the world’s oceans may alter foraging opportunities for tunas due to regional changes in prey abundances and compositions.
45 citations
TL;DR: The understanding of the bioenergetics and feeding dynamics of tunas on a global scale is reviewed, with an emphasis on yellowfin, bigeye, skipjack, albacore, and Atlantic bluefin tunas.
Abstract: Tunas are highly specialized predators that have evolved numerous adaptations for a lifestyle that requires large amounts of energy consumption. Here we review our understanding of the bioenergetics and feeding dynamics of tunas on a global scale, with an emphasis on yellowfin, bigeye, skipjack, albacore, and Atlantic bluefin tunas. Food consumption balances bioenergetics expenditures for respiration, growth (including gonad production), specific dynamic action, egestion, and excretion. Tunas feed across the micronekton and some large zooplankton. Some tunas appear to time their life history to take advantage of ephemeral aggregations of crustacean, fish, and molluscan prey. Ontogenetic and spatial diet differences are substantial, and significant interdecadal changes in prey composition have been observed. Diet shifts from larger to smaller prey taxa highlight ecosystem-wide changes in prey availability and diversity and provide implications for changing bioenergetics requirements into the future. Where tunas overlap, we show evidence of niche separation between them; resources are divided largely by differences in diet percentages and size ranges of prey taxa. The lack of long-term data limits the ability to predict impacts of climate change on tuna feeding behaviour. We note the need for systematic collection of feeding data as part of routine monitoring of these species, and we highlight the advantages of using biochemical techniques for broad-scale analyses of trophic relations. We support the continued development of ecosystem models, which all too often lack the regional-specific trophic data needed to adequately investigate climate and fishing impacts.
43 citations
TL;DR: This study provides compelling new evidence that diatoms are an important exception to temperature–size rules, and shows that interspecific effects were a bigger contributor to whole-community size differences, and are probably more ecologically important than more commonly studied intraspecific effects.
Abstract: Climate warming has been linked to an apparent general decrease in body sizes of ectotherms, both across and within taxa, especially in aquatic systems. Smaller body size in warmer geographical regions has also been widely observed. Since body size is a fundamental determinant of many biological attributes, climate-warming-related changes in size could ripple across multiple levels of ecological organization. Some recent studies have questioned the ubiquity of temperature-size rules, however, and certain widespread and abundant taxa, such as diatoms, may be important exceptions. We tested the hypothesis that diatoms are smaller at warmer temperatures using a system of geothermally heated streams. There was no consistent relationship between size and temperature at either the population or community level. These field data provide important counterexamples to both James' and Bergmann's temperature-size rules, respectively, undermining the widely held assumption that warming favours the small. This study provides compelling new evidence that diatoms are an important exception to temperature-size rules for three reasons: (i) we use many more species than prior work; (ii) we examine both community and species levels of organization simultaneously; (iii) we work in a natural system with a wide temperature gradient but minimal variation in other factors, to achieve robust tests of hypotheses without relying on laboratory setups, which have limited realism. In addition, we show that interspecific effects were a bigger contributor to whole-community size differences, and are probably more ecologically important than more commonly studied intraspecific effects. These findings highlight the need for multispecies approaches in future studies of climate warming and body size.
42 citations
Cites background from "Predicting marine phytoplankton com..."
...Keywords: Bergmann’s rule, climate change, community size structure, diatoms, global warming, James’ rule, phytobenthos, phytoplankton, temperature–size relationships, temperature–size rule Received 21 November 2012 and accepted 20 May 2013...
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...…observed towards smaller primary producer species at warmer temperatures in both mesocosm experiments (Lewandowska & Sommer 2010; Yvon-Durocher et al. 2011; Peter & Sommer 2012) and natural ecosystems (Li et al. 2009; Winder et al. 2009; Barnes et al. 2010), as predicted by Daufresne et al. (2009)....
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01 Jul 2015
TL;DR: In this paper, the authors analyzed remotely-sensed ocean color data at two spatial scales, one based on ecologically defined sub-units of the ecosystem and the other on a regular grid (0.5°).
Abstract: The spring phytoplankton bloom on the US Northeast Continental Shelf is a feature of the ecosystem production cycle that varies annually in timing, spatial extent, and magnitude. To quantify this variability, we analyzed remotely-sensed ocean color data at two spatial scales, one based on ecologically defined sub-units of the ecosystem (production units) and the other on a regular grid (0.5°). Five units were defined: Gulf of Maine East and West, Georges Bank, and Middle Atlantic Bight North and South. The units averaged 47×103 km2 in size. The initiation and termination of the spring bloom were determined using change-point analysis with constraints on what was identified as a bloom based on climatological bloom patterns. A discrete spring bloom was detected in most years over much of the western Gulf of Maine production unit. However, bloom frequency declined in the eastern Gulf of Maine and transitioned to frequencies as low as 50% along the southern flank of the Georges Bank production unit. Detectable spring blooms were episodic in the Middle Atlantic Bight production units. In the western Gulf of Maine, bloom duration was inversely related to bloom start day; thus, early blooms tended to be longer lasting and larger magnitude blooms. We view this as a phenological mismatch between bloom timing and the “top-down” grazing pressure that terminates a bloom. Estimates of secondary production were available from plankton surveys that provided spring indices of zooplankton biovolume. Winter chlorophyll biomass had little effect on spring zooplankton biovolume, whereas spring chlorophyll biomass had mixed effects on biovolume. There was evidence of a “bottom up” response seen on Georges Bank where spring zooplankton biovolume was positively correlated with the concentration of chlorophyll. However, in the western Gulf of Maine, biovolume was uncorrelated with chlorophyll concentration, but was positively correlated with bloom start and negatively correlated with magnitude. This observation is consistent with both a “top-down” mechanism of control of the bloom and a “bottom-up” effect of bloom timing on zooplankton grazing. Our inability to form a consistent model of these relationships across adjacent systems underscores the need for further research.
40 citations
Cites background from "Predicting marine phytoplankton com..."
...The timing may also influence the size spectra and species composition of the bloom due to the effects of thermal conditions when the bloom develops (Barnes et al., 2011; Mousing et al., 2014) or due to the light regime affecting early versus late blooms (Polimene et al., 2014)....
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Autonomous University of Barcelona1, Queensland University of Technology2, McGill University3, University of Tasmania4, University of Texas at Austin5, IFREMER6, Hobart Corporation7, University of British Columbia8, Spanish National Research Council9, Memorial University of Newfoundland10, University of New South Wales11, University of Queensland12, Commonwealth Scientific and Industrial Research Organisation13, University of California, Los Angeles14, Texas A&M University15, Potsdam Institute for Climate Impact Research16, National Oceanic and Atmospheric Administration17, Dalhousie University18
TL;DR: This article explored the mechanisms that underlie the diversity of responses to changes in temperature and LTLs in eight global marine ecosystem models from the Fisheries and Marine Ecosystem Model Intercomparison Project (FishMIP).
36 citations
References
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TL;DR: If the organisms are randomly distributed, a single count is sufficient to obtain an estimate of their abundance and confidence limits for this estimate, even if pipetting, dilution or concentration are involved.
Abstract: Various methods for the estimation of populations of algae and other small freshwater organisms are described. A method of counting is described in detail. It is basically that of Utermohl and uses an inverted microscope. If the organisms are randomly distributed, a single count is sufficient to obtain an estimate of their abundance and confidence limits for this estimate, even if pipetting, dilution or concentration are involved. The errors in the actual counting and in converting colony counts to cell numbers are considered and found to be small relative to the random sampling error. Data are also given for a variant of Utermohl's method using a normal microscope and for a method of using a haemocytometer for the larger plankton algae.
2,572 citations
"Predicting marine phytoplankton com..." refers background or methods in this paper
...Sub-samples (100 ml) were settled (Utermıhl technique (Lund et al. 1958)) and individuals counted at the species level with an inverted microscope....
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...technique (Lund et al. 1958)) and individuals counted at the species level with an inverted...
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TL;DR: Cellular carbon and nitrogen content and cell volume of nutritionally and morphologically diverse dinoflagellate species were measured to determine carbon to volume and nitrogen to volume relationships.
Abstract: Cellular carbon and nitrogen content and cell volume of nutritionally and morphologically diverse dinoflagellate species were measured to determine carbon to volume (C : vol) and nitrogen to volume (N : vol) relationships. Cellular C and N content ranged from 48 to 3.0 3 10 4 pgC cell 21 21 5
2,137 citations
"Predicting marine phytoplankton com..." refers background in this paper
...0 −− = µvolumeyearCpg Equation 5 reported for taxonomically diverse protist plankton (Menden-Deuer and Lessard 2000)....
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...reported for taxonomically diverse protist plankton (Menden-Deuer and Lessard 2000)....
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TL;DR: In this paper, an estimate of global net primary production in the ocean has been computed from the monthly mean near-surface chlorophyll fields for 1979-1986 obtained by the Nimbus 7 CZCS radiometer.
Abstract: An estimate of global net primary production in the ocean has been computed from the monthly mean near-surface chlorophyll fields for 1979-1986 obtained by the Nimbus 7 CZCS radiometer. Our model required information about the subsurface distribution of chlorophyll, the parameters of the photosynthesis-light relationship, the sun angle and cloudiness. The computations were partitioned among 57 biogeochemical provinces that were specified from regional oceanography and by examination of the chlorophyll fields. Making different assumptions about the overestimation of chlorophyll by the CZCS in turbid coastal areas, the global net primary production from phytoplankton is given as 45-50 Gt C year"1. This may be compared with current published estimates for land plants of 45-68 Gt C year"' and for coastal vegetation of 1.9 Gt C year"1.
1,381 citations
"Predicting marine phytoplankton com..." refers background or methods in this paper
...All changes from the implementation of Longhurst et al. (Longhurst et al. 1995) are detailed in Mélin (Mélin 2003)....
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...ocean area (Longhurst et al. 1995), and to regional differences in phytoplankton community...
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...PP was computed from a wavelength- and depthresolved model (Mélin 2003), building on the approach of Longhurst et al. (Longhurst et al. 1995)....
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...This is due to variations in absolute productivity among regions, with 50% of production estimated to come from 27% of ocean area (Longhurst et al. 1995), and to regional differences in phytoplankton community structure....
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...(Longhurst et al. 1995) are detailed in Mélin (Mélin 2003)....
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TL;DR: This study provides evidence that reduced body size is the third universal ecological response to global warming in aquatic systems besides the shift of species ranges toward higher altitudes and latitudes and the seasonal shifts in life cycle events.
Abstract: Understanding the ecological impacts of climate change is a crucial challenge of the twenty-first century. There is a clear lack of general rules regarding the impacts of global warming on biota. Here, we present a metaanalysis of the effect of climate change on body size of ectothermic aquatic organisms (bacteria, phyto- and zooplankton, and fish) from the community to the individual level. Using long-term surveys, experimental data and published results, we show a significant increase in the proportion of small-sized species and young age classes and a decrease in size-at-age. These results are in accordance with the ecological rules dealing with the temperature–size relationships (i.e., Bergmann's rule, James' rule and Temperature–Size Rule). Our study provides evidence that reduced body size is the third universal ecological response to global warming in aquatic systems besides the shift of species ranges toward higher altitudes and latitudes and the seasonal shifts in life cycle events.
1,292 citations
"Predicting marine phytoplankton com..." refers background in this paper
...There is evidence that reduced body size is the third universal ecological response to global warming besides the shift of species ranges toward higher altitudes and latitudes and the seasonal shifts in life-cycle events (Daufresne et al. 2009)....
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...higher altitudes and latitudes and the seasonal shifts in life-cycle events (Daufresne et al. 2009)....
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TL;DR: In this paper, the frequency distributions of particIe size between sizes of about I and 100 p are given for both surface and deep water of the Atlantic and Pacific Oceans.
Abstract: Frequency distributions of particIe size between sizes of about I and 100 p are given for both surface and deep water of the Atlantic and Pacific Oceans. The form of the size spectra varies predictably both geographically and with depth. A hypothesis is presented to show that, to a first approximation, roughly equal concentrations of material occur at all particle sizes within the range from 1 p to about 10” p, i.e. from bacteria to whales.
1,116 citations