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.
Citations
More filters
TL;DR: In this article, the authors investigated the feasibility of sustaining current and increased per capita fish consumption rates in 2050 and concluded that meeting current and larger consumption rates is feasible, despite a growing population and the impacts of climate change on potential fisheries production, but only if fish resources are managed sustainably and the animal feeds industry reduces its reliance on wild fish.
Abstract: Expansion in the world's human population and economic development will increase future demand for fish products. As global fisheries yield is constrained by ecosystems productivity and management effectiveness, per capita fish consumption can only be maintained or increased if aquaculture makes an increasing contribution to the volume and stability of global fish supplies. Here, we use predictions of changes in global and regional climate (according to IPCC emissions scenario A1B), marine ecosystem and fisheries production estimates from high resolution regional models, human population size estimates from United Nations prospects, fishmeal and oil price estimations, and projections of the technological development in aquaculture feed technology, to investigate the feasibility of sustaining current and increased per capita fish consumption rates in 2050. We conclude that meeting current and larger consumption rates is feasible, despite a growing population and the impacts of climate change on potential fisheries production, but only if fish resources are managed sustainably and the animal feeds industry reduces its reliance on wild fish. Ineffective fisheries management and rising fishmeal prices driven by greater demand could, however, compromise future aquaculture production and the availability of fish products.
374 citations
Cites background or methods from "Predicting marine phytoplankton com..."
...We estimated a from the total biomass density of phytoplankton and microzooplankton groups from ERSEM output and convert this to numerical density across a realistic size range (10 14 to 10 4 g) assuming a fixed slope b of 1, in keeping with global empirical studies of phytoplankton size spectra (Barnes et al., 2011)....
[...]
...…the total biomass density of phytoplankton and microzooplankton groups from ERSEM output and convert this to numerical density across a realistic size range (10 14 to 10 4 g) assuming a fixed slope b of 1, in keeping with global empirical studies of phytoplankton size spectra (Barnes et al., 2011)....
[...]
TL;DR: Five existing methods that address the needs of monitoring and assessment of marine ecosystems are reviewed, highlighting their main characteristics and analyzing their commonalities and differences.
Abstract: Traditional and emerging human activities are increasingly putting pressures on marine ecosystems and impacting their ability to sustain ecological and human communities. To evaluate the health status of marine ecosystems we need a science-based, integrated Ecosystem Approach, that incorporates knowledge of ecosystem function and services provided that can be used to track how management decisions change the health of marine ecosystems. Although many methods have been developed to assess the status of single components of the ecosystem, few exist for assessing multiple ecosystem components in a holistic way. To undertake such an integrative assessment, it is necessary to understand the response of marine systems to human pressures. Hence, innovative monitoring is needed to obtain data to determine the health of large marine areas, and in an holistic way. Here we review five existing methods that address both of these needs (monitoring and assessment): the Ecosystem Health Assessment Tool; a method for the Marine Strategy Framework Directive in the Bay of Biscay; the Ocean Health Index; the Marine Biodiversity Assessment Tool; and the Nested Environmental status Assessment Tool. We have highlighted their main characteristics and analyzing their commonalities and differences, in terms of: use of the Ecosystem Approach; inclusion of multiple components in the assessment; use of reference conditions; use of integrative assessments; use of a range of values to capture the status; weighting ecosystem components when integrating; determine the uncertainty; ensure spatial and temporal comparability; use of robust monitoring approaches; and address pressures and impacts. Ultimately, for any ecosystem assessment to be effective it needs to be: transparent and repeatable and, in order to inform marine management, the results should be easy to communicate to wide audiences, including scientists, managers and policymakers.
217 citations
Cites methods from "Predicting marine phytoplankton com..."
...…has long been used to monitor chlorophyll a (Coppini et al., 2012), it has only recently been applied to determine phytoplankton size structure (Barnes et al., 2011; Brewin et al., 2011), composition and functionality (Moisan et al., 2013; Palacz et al., 2013; Rousseaux et al., 2013) and…...
[...]
TL;DR: Warming may enhance phytoplankton losses to microzooplankton herbivory in eutrophic but not in oligotrophic waters, and the GAM analysis provides important insights into underlying system relationships and reasons why community-level responses in natural systems may depart from theory.
Abstract: We evaluated a hypothesis derived from the metabolic theory of ecology (MTE) that the ratio of microzooplankton herbivory (m) to phytoplankton growth (m) will arise in a warming ocean because of the different temperature dependencies of autotrophic and heterotrophic organisms. Using community-level growth and grazing data from dilution experiments, generalized additive models (GAMs) were constructed to describe the effects of temperature and chlorophyll on m:m. At low chlorophyll levels, m:m decreases with increasing temperature, whereas at high chlorophyll levels, m:m increases initially with temperature before reaching a peak and then declines. These complex responses of m:m result from mixed effects of temperature and chlorophyll on microzooplankton biomass (Bz), biomass-specific microzooplankton grazing rate (m:Bz), and phytoplankton growth rate (m). Bz decreases with rising temperature and increases with rising chlorophyll. m:Bz increases with temperature and decreases with chlorophyll. Nutrient-enriched growth rate of phytoplankton (mn) and m increase with increasing temperature and chlorophyll. Holding chlorophyll constant, the calculated activation energies of m:Bz and mn are 0.67 6 0.05 and 0.36 6 0.05 eV, respectively, both consistent with previous MTE estimates for heterotrophs and autotrophs. Our study indicates that warming may enhance phytoplankton losses to microzooplankton herbivory in eutrophic but not in oligotrophic waters. The GAM analysis also provides important insights into underlying system relationships and reasons why community-level responses in natural systems may depart from theory based on laboratory data and individual species.
125 citations
Cites background from "Predicting marine phytoplankton com..."
...Thus, as mean cell size of phytoplankton is well related to total chlorophyll (Chen and Liu 2010; Barnes et al. 2011), an increasing trend of ln mn with chlorophyll should be expected....
[...]
...Phytoplankton mean cell size, another factor affecting mn, is well correlated with total chlorophyll concentration (Chen and Liu 2010; Barnes et al. 2011)....
[...]
TL;DR: Predicted latitudinal shifts are, on average, reduced by 20% when species interactions are incorporated, compared to DBEM predictions, with pelagic species showing the greatest reductions.
Abstract: Climate change has already altered the distribution of marine fishes. Future predictions of fish distributions and catches based on bioclimate envelope models are available, but to date they have not considered interspecific interactions. We address this by combining the species-based Dynamic Bioclimate Envelope Model (DBEM) with a size-based trophic model. The new approach provides spatially and temporally resolved predictions of changes in species' size, abundance and catch potential that account for the effects of ecological interactions. Predicted latitudinal shifts are, on average, reduced by 20% when species interactions are incorporated, compared to DBEM predictions, with pelagic species showing the greatest reductions. Goodness-of-fit of biomass data from fish stock assessments in the North Atlantic between 1991 and 2003 is improved slightly by including species interactions. The differences between predictions from the two models may be relatively modest because, at the North Atlantic basin scale, (i) predators and competitors may respond to climate change together; (ii) existing parameterization of the DBEM might implicitly incorporate trophic interactions; and/or (iii) trophic interactions might not be the main driver of responses to climate. Future analyses using ecologically explicit models and data will improve understanding of the effects of inter-specific interactions on responses to climate change, and better inform managers about plausible ecological and fishery consequences of a changing environment.
114 citations
Cites background from "Predicting marine phytoplankton com..."
...Thus, the median and mean body sizes of phytoplankton decrease with decreasing rates of primary production (Barnes et al., 2011)....
[...]
TL;DR: It is shown that marine location can be inferred from animal tissues, and carbon isotope ratios can be used to identify the location of open ocean feeding grounds for any pelagic animals for which tissue archives and matching records of sea surface temperature are available.
Abstract: Knowing the distribution of marine animals is central to understanding climatic and other environmental influences on population ecology. This information has proven difficult to gain through capture-based methods biased by capture location. Here we show that marine location can be inferred from animal tissues. As the carbon isotope composition of animal tissues varies with sea surface temperature, marine location can be identified by matching time series of carbon isotopes measured in tissues to sea surface temperature records. Applying this technique to populations of Atlantic salmon (Salmo salar L.) produces isotopically-derived maps of oceanic feeding grounds, consistent with the current understanding of salmon migrations, that additionally reveal geographic segregation in feeding grounds between individual philopatric populations and age-classes. Carbon isotope ratios can be used to identify the location of open ocean feeding grounds for any pelagic animals for which tissue archives and matching records of sea surface temperature are available.
104 citations
References
More filters
TL;DR: The size spectrum of particulate material in seawater can be expressed as total particle volume versus the logarithm of particle diameter as discussed by the authors, which appears to be the most informative way to pres...
Abstract: The size spectrum of particulate material in seawater can easily be expressed as total particle volume versus the logarithm of particle diameter. This appears to be the most informative way to pres...
213 citations
"Predicting marine phytoplankton com..." refers background in this paper
...…between the logarithm of total abundance by cell mass class and the logarithm of cell mass, with individuals binned to cell mass classes irrespective of species identity (Sheldon and Parsons 1967)) and (4) the range of cell masses that encompass a given proportion of total biomass or production....
[...]
TL;DR: A model describing the dynamics of coupled size spectra is presented, to explain how coupling of predator and detritivore communities affects the scaling of log N vs. log m, and the model predictions are remarkably consistent with observed patterns of exploited ecosystems.
Abstract: 1. Widely observed macro-ecological patterns in log abundance vs. log body mass of organisms can be explained by simple scaling theory based on food (energy) availability across a spectrum of body sizes. The theory predicts that when food availability falls with body size (as in most aquatic food webs where larger predators eat smaller prey), the scaling between log N vs. log m is steeper than when organisms of different sizes compete for a shared unstructured resource (e.g. autotrophs, herbivores and detritivores; hereafter dubbed 'detritivores'). 2. In real communities, the mix of feeding characteristics gives rise to complex food webs. Such complexities make empirical tests of scaling predictions prone to error if: (i) the data are not disaggregated in accordance with the assumptions of the theory being tested, or (ii) the theory does not account for all of the trophic interactions within and across the communities sampled. 3. We disaggregated whole community data collected in the North Sea into predator and detritivore components and report slopes of log abundance vs. log body mass relationships. Observed slopes for fish and epifaunal predator communities (-1.2 to -2.25) were significantly steeper than those for infaunal detritivore communities (-0.56 to -0.87). 4. We present a model describing the dynamics of coupled size spectra, to explain how coupling of predator and detritivore communities affects the scaling of log N vs. log m. The model captures the trophic interactions and recycling of material that occur in many aquatic ecosystems. 5. Our simulations demonstrate that the biological processes underlying growth and mortality in the two distinct size spectra lead to patterns consistent with data. Slopes of log N vs. log m were steeper and growth rates faster for predators compared to detritivores. Size spectra were truncated when primary production was too low for predators and when detritivores experienced predation pressure. 6. The approach also allows us to assess the effects of external sources of mortality (e.g. harvesting). Removal of large predators resulted in steeper predator spectra and increases in their prey (small fish and detritivores). The model predictions are remarkably consistent with observed patterns of exploited ecosystems.
210 citations
"Predicting marine phytoplankton com..." refers background in this paper
...This information is necessary to predict phytoplankton production by size class in inputs to size-based models of production at higher trophic levels (Jennings et al. 2008; Blanchard et al. 2009)....
[...]
TL;DR: The analyses show that emerging ecological theory can be synthesized to set baselines for assessing human and climate impacts on global scales.
Abstract: We show how theoretical developments in macroecology, life-history theory and food-web ecology can be combined to formulate a simple model for predicting the potential biomass, production, size and trophic structure of consumer communities. The strength of our approach is that it uses remote sensing data to predict properties of consumer communities in environments that are challenging and expensive to sample directly. An application of the model to the marine environment on a global scale, using primary production and temperature estimates from satellite remote sensing as inputs, suggests that the global biomass of marine animals more than 10−5 g wet weight is 2.62×109 t (=8.16 g m−2 ocean) and production is 1.00×1010 t yr−1 (31.15 g m−2 yr−1). Based on the life-history theory, we propose and apply an approximation for distinguishing the relative contributions of different animal groups. Fish biomass and production, for example, are estimated as 8.99×108 t (2.80 g m−2) and 7.91×108 t yr−1 (2.46 g m−2 yr−1), respectively, and 50% of fish biomass is shown to occur in 17% of the total ocean area (8.22 g m−2). The analyses show that emerging ecological theory can be synthesized to set baselines for assessing human and climate impacts on global scales.
201 citations
"Predicting marine phytoplankton com..." refers background in this paper
...This information is necessary to predict phytoplankton production by size class in inputs to size-based models of production at higher trophic levels (Jennings et al. 2008; Blanchard et al. 2009)....
[...]
TL;DR: In this article, a model linking phytoplankton absorption to size classes (PSCs) was developed based on the observation that the absolute value of a ph (443) co-varies with the spectral slope of phytolankton absorbance in the range of 443-510 nm.
193 citations
"Predicting marine phytoplankton com..." refers background in this paper
...…classes using a single variable, the optical absorption by phytoplankton at 443 nm, which can be derived from the inversion of ocean colour data (Hirata et al. 2008) but a complementary approach is to identify general relationships between remotely-sensed environmental variables and the size…...
[...]
...inversion of ocean colour data (Hirata et al. 2008) but a complementary approach is to identify...
[...]
TL;DR: A general empirical model is presented that describes the dependence of algal photophysiology on both the community composition and the relative irradiance within the water column and it is anticipated that such photophysiological parameterizations can improve primary production models by providing estimates of primary production that are specific to different phytoplankton classes on large scale.
Abstract: We analyzed a large dataset of simultaneous measurements of phytoplankton pigments, spectral specific absorption coefficient for phytoplankton [a*(l)], and photosynthesis versus irradiance (P versus E) curve parameters to examine the possible relationships between phytoplankton community structure and photophysiological properties at large spatial scales. Data were collected in various regions, mostly covering the trophic gradient encountered in the world’s open ocean. The community composition is described in terms of biomass of three phytoplankton classes, determined using specific biomarker pigments. We present a general empirical model that describes the dependence of algal photophysiology on both the community composition and the relative irradiance within the water column (essentially reflecting photoacclimation). The application of the model to the in situ dataset enables the identification of vertical profiles of photophysiological properties for each phytoplankton class. The class-specific a*(l) obtained are consistent with results from the literature and with previous models developed for small and large cells, both in terms of the absolute values and the vertical patterns. Similarly, for the class-specific P versus E curve parameters, the magnitude and vertical distribution obtained with this method are coherent with previous observations. Large cells (mainly diatoms) may be more efficient in carbon storage than smaller cells, whereas their yield of light absorption is lower. We anticipate that such photophysiological parameterizations can improve primary production models by providing estimates of primary production that are specific to different phytoplankton classes on large scale.
187 citations
"Predicting marine phytoplankton com..." refers background in this paper
...For example, Uitz et al. (Uitz et al. 2006; Uitz et al. 2008) have determined size-spectra of phytoplankton communities from near-surface chlorophyll a concentration using accessory pigments as markers for pico, nano and micro-plankton to infer the column-integrated phytoplankton biomass, its…...
[...]