Pelagic Primary Production Research Articles

Explaining ecological shifts: the roles of temperature and primary production in the long‐term dynamics of benthic faunal composition

Predicting the ecological consequences of environmental change requires that we can identify the drivers of long‐term ecological variation. Biological assemblages can exhibit abrupt deviations from temporal trends, potentially resulting in irreversible shifts in species composition over short periods of time. Such dynamics are hypothesised to occur as gradual forcing eventually causes biological thresholds to be crossed, but could also be explained by biota simply tracking abrupt changes to their environment. Here, we modelled temporal variation in a North Sea benthic faunal assemblage over a 40‐year period (1972–2012) to test for changes to temporal trends of biota and determine whether they could be explained by underlying patterns in sea temperature and primary production. These extrinsic factors were postulated to influence community dynamics through their roles in determining and sustaining the metabolic demands of organisms, respectively. A subset of mainly large and long‐lived taxa (those loaded on the first principal component of taxa densities) exhibited two significant changes to their temporal trends, which culminated in a shift in assemblage composition. These changes were explained by an increase in pelagic primary production, and hence detrital food input to the seabed, but were unrelated to variation in sea temperature. A second subset of mainly small and short‐lived taxa (those loaded on the second principal component) did not experience any significant changes to their temporal trends, as enhanced pelagic primary production appeared to mitigate the impact of warming on these organisms. Our results suggest that abrupt ecological shifts can occur as biota track underlying variation in extrinsic factors, in this case primary production. Changes to the structure of ecosystems may therefore be predictable based on environmental change projections.

Plankton supports the majority of fish biomass on temperate rocky reefs

Coastal temperate rocky reefs are economically valuable and highly diverse, yet the trophodynamics of these productive systems are understudied. Quantifying the trophic linkages that support fish assemblages on these reefs is valuable for understanding how these assemblages may change due to changes in benthic and pelagic primary production. The goal of this study was to quantify the relative importance of primary sources of nutrition (here, macroalgae, phytoplankton, zooplankton, and detritus) for supporting fish assemblages on shallow rocky reefs. We constructed a general food web that traces the food sources supporting fish biomass on shallow temperate reefs near Sydney, Australia, using species composition data from 17 reefs based on field sampling and the Reef Life Survey (reeflifesurvey.com), and combined this with dietary information sourced from field collections and published literature. Planktivorous fish typically dominated reef fish assemblages, comprising an average of 41% of the total fish biomass (ranging from 12 to 71% among sites). Our food web analysis showed that, on average, 56% (±5% s.e.) of the total fish biomass was ultimately supported by phytoplankton (and 53% from zooplankton), in comparison to 31% (±4%) supported by macroalgae and 12% (±2%) by detritus. This result highlights the dominance of zooplanktivorous fish on temperate reefs and also their importance as prey for piscivores. Our findings demonstrate the importance of understanding the coastal dynamics of plankton and planktivory for predicting the response of temperate reefs and their fish assemblages to a changing climate.

A model-based analysis of physical and biological controls on ice algal and pelagic primary production in Resolute Passage

A coupled 1-D sea ice-ocean physical-biogeochemical model was developed to investigate the processes governing ice algal and phytoplankton blooms in the seasonally ice-covered Arctic Ocean. The 1-D column is representative of one grid cell in 3-D model applications and provides a tool for parameterization development. The model was applied to Resolute Passage in the Canadian Arctic Archipelago and assessed with observations from a field campaign during spring of 2010. The factors considered to limit the growth of simulated ice algae and phytoplankton were light, nutrients, and in the case of ice algae, ice melt. In addition to the standard simulation, several model experiments were conducted to determine the sensitivity of the simulated ice algal bloom to parameterizations of light, mortality, and pre-bloom biomass. Model results indicated that: (1) ice algae limit subsequent pelagic productivity in the upper 10 m by depleting nutrients to limiting levels; (2) light availability and pre-bloom biomass determine the onset timing of the ice algal bloom; (3) the maximum biomass is relatively insensitive to the pre-bloom biomass, but is limited by nutrient availability; (4) a combination of linear and quadratic parameterizations of mortality rate is required to adequately simulate the evolution of the ice algal bloom; and (5) a sinking rate for large detritus greater than a threshold of ∼10 m d–1 effectively strips the surface waters of the limiting nutrient (silicate) after the ice algal bloom, supporting the development of a deep chlorophyll maximum.

Significance of pelagic and benthic metabolism for the carbon budget of a shallow lake

Pelagic and benthic primary production and respiration were measured at an offshore station in the shallow, 1.2 m deep, polymictic Lake Gardno (Poland) to examine the role of the pelagic zone and the sediments in the overall carbon budget of this lake. The respiration rates in the sediments were within the same range of values as those in the pelagic zone. The results indicate that although the pelagic zone of the lake was net autotrophic (P:R = 2.46) based on annual cycles, total primary production to respiration (pelagic zone + sediments) was balanced, and the P:R ratio was 1.18. Thus, potentially only a small part of pelagic primary production is exported and buried in the sediments. The whole lake ecosystem does not act as an effective atmospheric CO2 sink. The balanced primary production to respiration ratio in the open water zone of the lake indicated that littoral production was most probably decomposed or buried within the littoral zone.

Relación entre la producción primaria y bacteriana pelágicas en dos lagunas húmicas vegetadas

In this study, we show that depth-integrated pelagic primary production (PP) can exceed bacterioplankton production (BP) in vegetated humic shallow lakes, giving as a result an autotrophic water column, despite light restrictions and availability of organic carbon for lake bacteria. Intuitively, these conditions should favor the development of a heterotrophic water column. Instead, during our survey, BP represented between 1.3 to 5% of PP most of the time. Only once, during late summer, BP was ~71% of PP. Although we cannot conclude about the mechanisms behind the observed results, previous surveys and experimentation in the wetland allow us to hypothesize that autotrophic conditions were favored by: i) the shallow nature of the lakes, which compensates for light attenuation by organic matter when integrating production in the water column, ii) the presence of anaerobic anoxygenic photosynthetic bacteria below the macrophyte cover, and iii) high predation rates on bacterioplankton by heterotrophic flagellates below the floating plants.

A numerical study of the benthic–pelagic coupling in a shallow shelf sea (Gulf of Trieste)

A coupled physical–biogeochemical 1D model (BFM–POM 1D) with an intermediate complexity benthic formulation was used to carry out sensitivity tests on the coupling parameters (sedimentation and diffusion at the sediment–water interface). Moreover, a mechanistic experiment was designed to investigate the role of filter feeders in regulating the biogeochemical state of the system in a coastal sea. Best reference parameters of sedimentation and diffusion were chosen from the sensitivity experiments carried out based on available observations. The mechanistic experiment revealed the importance of filter feeders’ role in trapping pelagic organic matter and regulating benthic–pelagic nutrient fluxes, as well as controlling pelagic primary production. The model demonstrated to be able to qualitatively reproduce the biogeochemical characteristics of the system and adapt to different trophic configurations. The results shown are encouraging and foresee its possible use as a tool to study causal relationships and help in finding solutions for management issues.

In-situ measured primary productivity of ice algae in Arctic sea ice floes using a new incubation method

Recent changes in climate and environmental conditions have had great negative effects such as decreasing sea ice thickness and the extent of Arctic sea ice floes that support ice-related organisms. However, limited field observations hinder the understanding of the impacts of the current changes in the previously ice-covered regions on sea ice algae and other ice-related ecosystems. Our main objective in this study was to measure recent primary production of ice algae and their relative contribution to total primary production (ice plus pelagic primary production). In-situ primary productivity experiments with a new incubation system for ice algae were conducted in 3 sea ice cores at 2 different ice camps in the northern Chukchi Sea, 2014, using a 13C and 15N isotope tracer technique. A new incubation system was tested for conducting primary productivity experiments on ice algae that has several advantages over previous incubation methods, enabling stable carbon and nitrogen uptake experiments on ice algae under more natural environmental conditions. The vertical C-shaped distributions of the ice algal chl-a, with elevated concentrations at the top and bottom of the sea ice were observed in all cores, which is unusual for Arctic sea ice. The mean chl-a concentration (0.05 ± 0.03 mg chl-a m−3) and the daily carbon uptake rates (ranging from 0.55 to 2.23 mg C m−2 d−1) for the ice algae were much lower in this study than in previous studies in the Arctic Ocean. This is likely because of the late sampling periods and thus the substantial melting occurring. Ice algae contributed 1.5–5.7% of the total particulate organic carbon (POC) contents of the combined euphotic water columns and sea ice floes. In comparison, ice algae contributed 4.8–8.6% to the total primary production which is greater than previously reported in the Arctic Ocean. If all of the ice-associated productions were included, the contributions of the sea ice floes to the total primary production would be greater in the Arctic Ocean and their importance would be greater in the arctic marine ecosystems.

Primary production enhancement in a shallow seamount (Gorringe — Northeast Atlantic)

Gorringe bank is a shallow seamount having its summit within the euphotic layer. The purpose of this study was to test the hypothesis that the interaction of ocean currents with shallow water seamounts, as the Gorringe, has a significant effect on local upwelling and primary production. Three hydrographic surveys were carried out: one in autumn (October 2011) and two in summer (June and July 2012). Physical (salinity, temperature), chemical (nutrients, dissolved oxygen, pH, total alkalinity and suspended particulate matter) and biological (chlorophyll, pelagic primary production and phytoplankton composition and abundance) variables were measured and/or determined in the area of Gorringe Bank, in particular over and around the Ormonde and Gettysburg peaks. Multivariate analyses (PCA and MDS) were applied to environmental and phytoplankton data. Statistical analysis of historical satellite and model data was also carried out in order to analyze local hydrographic conditions and to compare sea surface temperature and chlorophyll concentrations over the peaks and off the peaks in different seasons. Pelagic primary production, measured by Dissolved Oxygen methodology, reached values up to 24.10mgCm−3h−1 in the vicinity of the peaks. Phytoplankton abundance ranged from 2.2×103 to 14×103cellsL−1, being the community composed mainly of chain-forming Diatoms like Chaetoceros sp., Dactyliosolen spp., Hemiaulus hauckii and Pseudonitzschia spp., in summer months, in zones of high hydrodynamics of the peaks. By contrast, at locations away of the seamount summits and in autumn, Coccolithophores species reached the same or higher percentage in total abundance than Diatoms, being Discosphaera tubifer and Calcidiscus leptoporus cf. the most abundant species. The combined results indicate the presence of a seasonal effect of Gorringe summits on local upwelling and enhancement of primary production reflected in higher abundance of phytoplankton in the vicinity of the peaks, with emphasis on the Gettysburg, and higher surface chlorophyll concentrations. Therefore, obtained results support the hypothesis of production enhancement.

Primary production in the tropical continental shelf seas bordering northern Australia

Pelagic primary production (14C uptake) was measured 81 times between 1990 and 2013 at sites spanning the broad, shallow Northern Australian Shelf (NAS; 120−145°E) which borders the Australian continent. The mean of all areal production measurements was 1048±109mgCm−2d−1 (mean±95% CI). Estimates of areal primary production were correlated with integral upper-euphotic zone chlorophyll stocks (above the 50% and 20% light penetration depths) accessible to ocean color remote sensing and total water column chlorophyll standing crop, but not surface (0–2m) chlorophyll concentrations. While the NAS is subject to a well characterized monsoonal climate regime (austral summer-NW monsoon -wet: austral winter- SE monsoon -dry), most seasonal differences in means of regional-scale chlorophyll standing crop (11–33mg Chlm−2 for 12 of 15 season-region combinations) and areal primary production (700–1850mgCm−day−1 for 12 of 15 season-region combinations) fell within a 3−fold range. Apart from the shallow waters of the Torres Strait and northern Great Barrier Reef, picoplankton (<2µm size fraction) dominated chlorophyll standing crop and primary production with regional means of picoplankton contributions ranging from 45 to >80%. While the range of our post-1990 areal production estimates overlaps the range of production estimates made in NAS waters during 1960–62, the mean of post-1990 estimates is over 2-fold greater. We regard the difference to be due to improvements in production measurement techniques, particularly regarding the reduction of potential metal toxicity and incubations in more realistic light regimes.

Importance of coastal primary production in the northern Baltic Sea.

In this study, we measured depth-dependent benthic microalgal primary production in a Bothnian Bay estuary to estimate the benthic contribution to total primary production. In addition, we compiled data on benthic microalgal primary production in the entire Baltic Sea. In the estuary, the benthic habitat contributed 17 % to the total annual primary production, and when upscaling our data to the entire Bothnian Bay, the corresponding value was 31 %. This estimated benthic share (31 %) is three times higher compared to past estimates of 10 %. The main reason for this discrepancy is the lack of data regarding benthic primary production in the northern Baltic Sea, but also that past studies overestimated the importance of pelagic primary production by not correcting for system-specific bathymetric variation. Our study thus highlights the importance of benthic communities for the northern Baltic Sea ecosystem in general and for future management strategies and ecosystem studies in particular.Electronic supplementary materialThe online version of this article (doi:10.1007/s13280-016-0778-5) contains supplementary material, which is available to authorized users.

Dietary Reliance on Benthic Primary Production as a Predictor of Mercury Accumulation in Freshwater Fish and Turtles

The feeding ecology of a species can affect the transfer and accumulation of contaminants such as mercury (Hg). Modeling the accumulation of Hg through food webs can help identify which animals are likely to be burdened by elevated Hg concentrations. In lakes, most of the Hg is sequestered in the sediments. Therefore, species ultimately relying on benthic primary production may experience a greater trophic transfer of Hg relative to species that rely on pelagic primary production. This hypothesis was tested in a simple food web using muscle tissue collected from three species of fish (Lepomis gibbosus, Notropis heterodon, and Labidesthes sicculus) and blood from two species of turtles (Sternotherus odoratus and Chrysemys picta) that differ in reliance on benthic primary production. Averaged multiple linear regression models were used to predict Hg concentrations in the five consumers with respect to reliance on benthic primary production, while controlling for other factors known to influence Hg accumulation (sex, size, lake, species identity, and trophic level). A positive and significant relationship was found between Hg burden and dietary reliance on benthic primary production, animal length, trophic level, and species identity in fish. In turtles, the relationship between Hg burden and dietary reliance on benthic primary production was not significant, but trophic level, animal length, and species identity significantly influenced Hg burden. Overall, reliance on benthic primary production was an important predictor of Hg burden for fish, but not for turtles. Future attempts to model Hg accumulation in similar study systems and/or fish species should include dietary reliance on benthic primary production as a predictor variable.

Phytoplankton Productivity in an Arctic Fjord (West Greenland): Estimating Electron Requirements for Carbon Fixation and Oxygen Production.

Accurate quantification of pelagic primary production is essential for quantifying the marine carbon turnover and the energy supply to the food web. Knowing the electron requirement (Κ) for carbon (C) fixation (Κ C) and oxygen (O2) production (Κ O2), variable fluorescence has the potential to quantify primary production in microalgae, and hereby increasing spatial and temporal resolution of measurements compared to traditional methods. Here we quantify Κ C and Κ O2 through measures of Pulse Amplitude Modulated (PAM) fluorometry, C fixation and O2 production in an Arctic fjord (Godthåbsfjorden, W Greenland). Through short- (2h) and long-term (24h) experiments, rates of electron transfer (ETRPSII), C fixation and/or O2 production were quantified and compared. Absolute rates of ETR were derived by accounting for Photosystem II light absorption and spectral light composition. Two-hour incubations revealed a linear relationship between ETRPSII and gross 14C fixation (R2 = 0.81) during light-limited photosynthesis, giving a Κ C of 7.6 ± 0.6 (mean ± S.E.) mol é (mol C)−1. Diel net rates also demonstrated a linear relationship between ETRPSII and C fixation giving a Κ C of 11.2 ± 1.3 mol é (mol C)−1 (R2 = 0.86). For net O2 production the electron requirement was lower than for net C fixation giving 6.5 ± 0.9 mol é (mol O2)−1 (R2 = 0.94). This, however, still is an electron requirement 1.6 times higher than the theoretical minimum for O2 production [i.e. 4 mol é (mol O2)−1]. The discrepancy is explained by respiratory activity and non-photochemical electron requirements and the variability is discussed. In conclusion, the bio-optical method and derived electron requirement support conversion of ETR to units of C or O2, paving the road for improved spatial and temporal resolution of primary production estimates.

The ecological history of Lake Ontario according to phytoplankton

Abstract Lake Ontario's condition has fluctuated since European settlement, and our understanding of the linkages between observed ecosystem shifts and stressors is improving. Changes in the physical and chemical environment of the lake due to non-indigenous species, pollution, sedimentation, turbidity, and climate change altered the pelagic primary producers, so algal assessments have been valuable for tracking long-term conditions. We present a chronological account of algal assessments to summarize past and present environmental conditions in Lake Ontario. This review particularly focuses on pelagic, diatom-based assessments as their fossils in sediments have revealed the combined effects of environmental insults and recovery. This review recaps the long-term trends according to three unique regions: Hamilton Harbour, the main lake basin, and the Bay of Quinte. We summarize pre-European impact settlement; eutrophication throughout most of the 20th century; subsequent water quality changes due to nutrient reductions; and filter-feeding dreissenid colonization and contemporary pelagic, shoreline, and embayment impairments. Recent data suggest that although phytoplankton biovolume is stable, species composition has shifted to an increase in densities of spring eutrophic diatoms and summer cyanobacteria. Continued monitoring and evaluation of historical data will assist in understanding and responding to the natural and anthropogenic drivers of Lake Ontario's environmental conditions.

Phosphorus Availability Alters the Effects of Silver Nanoparticles on Periphyton Growth and Stoichiometry.

Exposure to silver nanoparticles (AgNPs) may alter the structure and function of freshwater ecosystems. However, there remains a paucity of studies investigating the effects of AgNP exposure on freshwater communities in the natural environment where interactions with the ambient environment may modify AgNP toxicity. We used nutrient diffusing substrates to determine the interactive effects of AgNP exposure and phosphorus (P) enrichment on natural assemblages of periphyton in three Canadian Shield lakes. The lakes were all phosphorus poor and spanned a gradient of dissolved organic carbon availability. Ag slowly accumulated in the exposed periphyton, which decreased periphyton carbon and chlorophyll a content and increased periphyton C:P and N:P in the carbon rich lakes. We found significant interactions between AgNP and P treatments on periphyton carbon, autotroph standing crop and periphyton stoichiometry in the carbon poor lake such that P enhanced the negative effects of AgNPs on chlorophyll a and lessened the impact of AgNP exposure on periphyton stoichiometry. Our results contrast with those of other studies demonstrating that P addition decreases metal toxicity for phytoplankton, suggesting that benthic and pelagic primary producers may react differently to AgNP exposure and highlighting the importance of in situ assays when assessing potential effects of AgNPs in fresh waters.

Particle sources and downward fluxes in the eastern Fram strait under the influence of the west Spitsbergen current

The carbon cycle of the Arctic Ocean is tightly regulated by land–atmosphere–cryosphere–ocean interactions. Characterizing these environmental exchanges and feedbacks is critical to facilitate projections of the carbon cycle under changing climate conditions. The environmental drivers of sinking particles including organic carbon (OC) to the deep-sea floor are investigated with four moorings including sediment traps and currentmeters at the Arctic gateway in the eastern Fram Strait, which is the area where warm anomalies are transported northwards to the Arctic. Particles fluxes were collected over one year (July 2010–July 2011) and have been analysed to obtain the content of the lithogenic fraction, calcium carbonate, OC and its stable isotopes, opal, and the grain size. Records of near bottom current speed and temperature along with satellite observations of sea ice extent and chlorophyll-a concentration have been used for evaluation of the environmental conditions.We found increased lithogenic fluxes (up to 9872mgm−2d−1) and coarsening grain size of settling particles in late winter–early spring. At the same time, intensifications of the northward flowing west Spitsbergen current (WSC) were recorded. The WSC was able to resuspend and transport northwards sediments that were deposited at the outlet of Storfjordrenna and on the upper slope west of Spitsbergen. The signal of recurrent winnowing of fine particles was also detected in the top layer of surface sediments. In addition, an increased arrival of sea ice transported ice rafted detritus (>414 detrital carbonate mineral grains larger than 1mm per m2) from the southern Spitsbergen coast along with terrestrial organic matter was observed beyond 1000m of water depth during winter months. Finally, the downward particle fluxes showed typical temporal variability of high latitudes, with high percentages of the biogenic compounds (opal, organic carbon and calcium carbonate) linked to the phytoplankton bloom in spring–summer. However, on an annual basis local planktonic production was a secondary source for the downward OC, since most of the OC was advected laterally by the WSC. Overall, these observations demonstrated the sensitivity of the downward flux of particles to environmental conditions such as hydrodynamics, sea ice rafting, and pelagic primary production. Future alteration of the patterns of natural drivers due to climate change is thus expected to cause major shifts in the downward flux of particles, including carbon, to the deep sea ecosystems.

Trematode infections reduce clearance rates and condition in blue mussels Mytilus edulis

Suspension feeders are important players in coastal food webs: by filtering particles suspended in the water column and depositing faeces and pseudofaeces in sediments, they mediate the coupling of pelagic primary and benthic secondary production. However, the potential interference of parasite infections on suspension feeding is not well investigated. We experimentally determined the effect of infections with metacercariae of the common trematode Renicola roscovita on clearance rates and condition of blue mussels Mytilus edulis. We also investigated whether there were differences in the effects of infections between different size classes of mussels. Using controlled infections under lab conditions, our experiment showed that infections significantly reduced the clearance rates of mussels. This effect was less pronounced in small (42% reduction) than in large mussels (71%). In addition, infections significantly reduced mussel body mass index in large (23% reduction) and small (17%) mussels compared to uninfected mussels. These reductions most likely resulted from a combined effect of an interference of the parasites with the mussel’s feeding apparatus (with the palps being the preferred infection site of the parasite) and of the energetic demands of the parasites (with metacercariae growing in size after initial infection). These negative effects on mussel filter feeding capacity indicate that parasites can alter a crucially important functional trait of marine suspension feeders.

Multiple environmental changes induce interactive effects on bacterial degradation activity in the Arctic Ocean

AbstractThe Arctic Ocean faces multiple environmental changes induced by climate change on both global and regional scale. In addition to global changes in seawater temperature and pH, Arctic waters receive organic matter enrichment due to increasing pelagic primary production, enhanced sea ice melting and increasing terrestrial carbon loads. We experimentally tested individual and combined effects of warming, acidification and organic matter amendment on growth, biomass production and extracellular enzyme activities of bacterioplankton in Fram Strait during early summer. Results reveal pH optima of 6.7–7.6 for extracellular leucine‐aminopeptidase and below pH 6.0 for beta‐glucosidase in the West Spitsbergen Current. These optima well below the current seawater pH imply increasing hydrolytic activity with ongoing ocean acidification. However, the new synthesis of extracellular enzymes during 4‐d incubations obscured the biochemical pH effects. Elevated temperature and carbohydrate supply had strongly interactive effects on bacterial biomass production in both Atlantic Water of the West Spitsbergen Current and Polar Water of the East Greenland Current. Activation energies ranged from 45 kJ mol−1 to 52 kJ mol−1 at in situ substrate concentration, while substantially higher values of 122–174 kJ mol−1 could be estimated from incubations with carbohydrate addition. The net loss of total amino acids in carbohydrate‐amended incubations was significantly reduced at elevated temperature in all experiments, suggesting enhanced de novo synthesis. Our findings show that the complexity of combined effects must be considered to better assess the potential of climate change to alter biogenic carbon and energy fluxes in marine systems.

Sediment oxygen consumption and benthic organic carbon mineralization on the continental shelves of the East China Sea and the Yellow Sea

Sediment oxygen consumption (SOC) rates on the shelves of the East China Sea (ECS) and the Yellow Sea (YS) were measured during five field studies in the period April 2010 to May 2011, using the batch intact core incubation technique. The measured SOC rates ranged from 1.73 to 17.56mmol O2m−2d−1, which are comparable to values reported for other typical continental shelves worldwide. For the shelves of both the ECS and the YS there was a remarkable spatial and temporal variation in SOC rates. SOC was used as a proxy to assess the benthic organic carbon mineralization in the ECS and the YS, and to prepare simple organic carbon budget. For the YS it was found that on average approximately 90% of the organic carbon derived from primary productivity was decomposed in the water column and 8% was decomposed in the sediment, resulting in <4% being permanently buried in the YS sediment. In contrast, approximately 70% of the organic carbon derived from primary productivity was decomposed in the water column in the ECS and 17% was decomposed in the sediment, suggesting that the permanently buried percentage (14%, relative to the primary productivity) was higher in the ECS. The contrasting contributions of benthic mineralization to the organic carbon cycle in the ECS and the YS indicated that there is tight coupling between pelagic and benthic biogeochemical processes in the ECS, but in the YS, the regenerated production and external non-marine nutrients regulated pelagic primary production.

Spatial patterns and environmental drivers of benthic infaunal community structure and ecosystem function on the New Zealand continental margin

To investigate regional drivers of spatial patterns in macro- and meio-faunal community structure (abundance, biomass and taxonomic diversity) and ecosystem function (sediment community oxygen consumption [SCOC]), we sampled two regions in close proximity on New Zealand's continental margin—the Chatham Rise and the Challenger Plateau. Sites (n = 15) were selected in water depths ranging from 266–1212 m to generate a gradient in sedimentary properties and, in particular, surface pelagic productivity. Both macro- and meio-fauna abundance and biomass was 2–3.5 times higher on the Chatham Rise than on the Challenger Plateau, reflecting regional differences in pelagic primary production. We also found significant inter- and intra-regional differences in macro-fauna taxonomic diversity with two distinctive site groupings in each region. Univariate and multivariate measures of macro-fauna community attributes were most strongly correlated with sediment photosynthetic pigment (explaining 24%–59% of the variation). Sediment pigment content was as equally important in explaining meio-fauna community structure (36%–7%). Unlike community structure, SCOC was most strongly correlated with depth (44%), most likely reflecting temperature effects on benthic metabolism. Our results highlight the importance of a benthic labile food supply in structuring infaunal communities on continental margins and emphasise a tight coupling between pelagic and benthic habitats.

Seasonal and interannual phytoplankton production in a sub-Arctic tidewater outlet glacier fjord, SW Greenland

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 524:27-38 (2015) - DOI: https://doi.org/10.3354/meps11174 Seasonal and interannual phytoplankton production in a sub-Arctic tidewater outlet glacier fjord, SW Greenland Thomas Juul-Pedersen1,*, Kristine E. Arendt1, John Mortensen1, Martin E. Blicher1, Dorte H. Søgaard1,3, Søren Rysgaard1,2,4 1Greenland Climate Research Centre, Greenland Institute of Natural Resources, PO Box 570, 3900 Nuuk, Greenland 2Centre for Earth Observation Science, CHR Faculty of Environment Earth and Resources, University of Manitoba, 499 Wallace Building, Winnipeg, MB R3T 2N2, Canada 3University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark 4Arctic Research Centre, Aarhus University, C. F. Møllers Allé 8, 8000 Aarhus C, Denmark *Corresponding author: thpe@natur.gl ABSTRACT: This study describes seasonal patterns and proposes likely drivers of an unusual phytoplankton primary production pattern in the outer-sill region of a tidewater outlet glacier-influenced fjord (Godthåbsfjord) in SW Greenland. It is based on monthly measurements of pelagic primary production and hydrographic conditions during a 7 yr period. Total annual primary production during 2005 to 2012 was between 84.6 and 139.1 g C m-2 yr-1. Two phytoplankton blooms of similar magnitude reoccur in the fjord every year. A ‘classical’ spring bloom of up to 1743 mg C m-2 d-1 occurred in late April/early May in a water column almost fully mixed due to tidal forces at the fjord sill. After the spring bloom, primary production decreased in June, after which a summer bloom of up to 1383 mg C m-2 d-1 built up. This bloom coincided with the development of a pycnocline caused by substantial runoff from the Greenland Ice Sheet every year during midsummer. This observation supports a hypothesis that fjord circulation modes and subglacial freshwater discharge, leading to upwelling of nutrient rich water, stimulate primary production in the fjord. Future changes in the timing or magnitude of meltwater runoff from the Greenland Ice Sheet are thus likely to affect phytoplankton dynamics in the fjord. KEY WORDS: Phytoplankton production · Seasonal patterns · Time series · Glacial meltwater · Sub-Arctic fjord · Greenland Full text in pdf format PreviousNextCite this article as: Juul-Pedersen T, Arendt KE, Mortensen J, Blicher ME, Søgaard DH, Rysgaard S (2015) Seasonal and interannual phytoplankton production in a sub-Arctic tidewater outlet glacier fjord, SW Greenland. Mar Ecol Prog Ser 524:27-38. https://doi.org/10.3354/meps11174 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 524. Online publication date: March 30, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.