The Baltic Sea is a severely disturbed marine ecosystem previously used as a dumping ground for chemical warfare agents (CWA), which are now known to enter its food web. We have performed a modelling ...exercise using a calibrated and validated Central Baltic Ecopath with Ecosim (EwE) model to recreate the potential environmental pathways of the infamous Clark I (diphenylchlorarsine). Observations from modelling timestamps covering recent times correspond with in situ detections in sediments and Atlantic cod (Gadus morhua). Under applied modelling conditions and scenarios, there is an active transfer of Clark I from sediments through the Baltic Sea food-web. According to our results, Clark I bioaccumulates within the Baltic Sea food web exclusively throughout the detritus-based food chain. The EwE model for the Central Baltic Sea also allows the simulation of changes in the food web under multiple anthropogenic stressors and management efforts, including recommendations from the Helsinki Commission Baltic Sea Action Plan (HELCOM BSAP). Among all investigated scentarios and factors, the commercial fishing is the most impactful on Clark I accumulation rate and contamination transfer within the Baltic Sea food web. The study indicates the need to extend the existing monitoring approach by adding additional species representing a broader range of ecological niches and tiers within the food chains. From the environmental perspective, the remediation of Chemical Weapons by removal should be considered as part of the integrated management of the Baltic Sea.
Display omitted
•The modelling exercise simulated potential pathways and forecasts for Clark I transfer within the Baltic Sea food web.•Observations from the modelling timestamps covering recent times correspond with in situ detections.•Remediation of Chemical Weapons by removal should be considered as part of the integrated management of the Baltic Sea.
Benthic fluxes of oxygen and carbon in coastal zones are poorly resolved in mechanistic models due to the lack of understanding of the diverse interactions among the physical, chemical, and ...biological drivers of biogeochemical fluxes. To inform modelling efforts we used ex-situ incubation experiments to identify spatial and seasonal patterns of oxygen and dissolved inorganic and organic carbon (DIC and DOC) fluxes in the coastal southern Baltic Sea. We used boosted regression trees to identify important drivers of the studied fluxes. Our results demonstrate that benthic communities, in addition to sediment parameters, played a dominant role in shaping oxygen and DIC fluxes, while neither benthic community, environment, season, nor sampling location could account for the highly variable DOC fluxes. DIC fluxes were partly decoupled from oxygen fluxes, since carbonate dissolution, anaerobic respiration, and submarine groundwater discharge affected DIC fluxes in the study region. Boosted regression trees proved to be a useful tool to study drivers of biogeochemical fluxes as it allowed to identify non-linear effects of biological and environmental variables on benthic fluxes.
Benthic food‐web structure and organic matter (OM) utilization are important for marine ecosystem functioning. In response to environmental changes related to the ongoing climate change, however, ...many benthic species are shifting their ranges to colder regions, which may lead to altered community composition, but it remains largely unknown how it will affect ecosystem functioning. Here, stable isotope analysis was used to study benthic OM utilization and food‐web structure and to assess whether their spatial patterns reflect today's community differentiation among biogeographic regions and depth zones. Benthic fauna and OM mixtures were collected from two depth zones (100–150 m vs. 200–250 m) within a temperate, two sub‐Arctic, and an Arctic fjord along a latitudinal gradient (59–78° N) that was used as a space‐for‐time substitution to assess the impact of climate change. Our results showed that Arctic and temperate communities are functionally different. Arctic communities were characterized by a strong resource partitioning among different feeding types, irrespective of depth zone. In contrast, all feeding types in temperate communities seemed to rely on sedimentary OM. The sub‐Arctic presented a transition zone. In the sub‐Arctic, shallower communities resembled Arctic communities, suggesting a functional transition between temperate and sub‐Arctic regions. Deeper sub‐Arctic communities resembled temperate communities, suggesting a functional transition between the sub‐Arctic and Arctic regions. This implies that the regions north of the current transitions (deep Arctic and shallow sub‐Arctic) are most likely to experience functional changes related to an altered OM utilization in benthic food webs in response to climate change.
Arctic benthic communities show a strong resource partitioning among different feeding types, while all feeding types in temperate communities rely on sedimentary organic matter. The sub‐Arctic presents a transition zone, with shallower communities resembling Arctic communities and deeper sub‐Arctic communities resembling temperate communities. This implies that the regions north of the current transitions (deep Arctic and shallow sub‐Arctic) are most likely to experience functional changes related to an altered organic matter utilization in benthic food webs in response to climate change.
The early development of many benthic invertebrates involves planktonic larval stages enabling larvae to disperse over large distances and to utilize food from the productive upper water layers. ...Although many past studies have recognized the importance of this period in the benthic life cycle, knowledge of larval distribution in time and space remains limited, especially for high-latitude regions with pronounced seasonal variability in environmental conditions. Here, we present the first inventory of meroplankton over the continental shelf in the Lofoten–Vesterålen region, northern Norway, over a full annual cycle. Six stations were sampled during 8 sampling events between September 2013 and August 2014. We recorded a total of 65 taxa, a considerably higher diversity than reported in studies from more northern regions. We observed a distinct seasonal pattern with characteristic meroplankton communities defining the seasons: spring, summer, and winter. Abundance and diversity during winter was low, with higher values in spring, and maximum abundances for most taxa in summer. Meroplankton community patterns did not reflect weak environmental spatial structure. Particle tracking was used to identify source and settlement locations of spring and summer communities. Spring and summer communities originated from shore and shelf areas, respectively. Larvae were generally transported toward Andfjord and adjacent shelf regions, irrespective of season. This spatially restricted dispersal and larval settlement highlights the importance of the local benthic communities for the resilience of the ecosystem.
•Spatial and temporal variability of benthic isotopic niches were investigated.•Food web structure follows the patterns of organic matter quantity and quality.•Higher organic matter supply supports ...food web diversity and benthic carnivory.•Spatio-temporal food-web structure is a good indicator of ecosystem function.
The quantity and quality of organic matter (OM) available for macrobenthos vary on temporal and spatial scale, especially in coastal areas, where the seafloor is supplied by both seasonal pulses of primary production and terrestrial carbon transported by rivers. Human-induced environmental changes will alter OM transport to the seafloor, thus, it is of crucial importance to recognize the impacts of spatio-temporal OM variability on macrobenthic food webs. In this study, the seasonal variability of quantity and quality of OM and its effect on benthic food-web structure were studied at four locations along the southern coast of the Baltic Sea, characterized by similar species pools but different environmental settings and various scales of anthropogenic and riverine influence. Our study shows that temporal changes in the isotopic niche (δ13C and δ15N) of benthic invertebrates follow the patterns of quantity and quality of OM related to seasonal changes of pelagic primary production, riverine discharge of terrestrial OM and the input of anthropogenically enriched sources. In the semi-enclosed bay, exposed to intensive summer blooms, all feeding groups expressed lower δ15N values in autumn, suggesting the incorporation of δ15N-depleted cyanobacteria. At a location supplied by a higher proportion of OM from allochthonous sources (riverine discharge), omnivores occupied higher trophic levels, probably due to a higher abundance of meiobenthic prey. In contrast, at the open Polish coast, where the main food supply occurs during diatom spring bloom, the isotopic niche of omnivorous species showed much higher seasonal variability, underlining the importance of food availability for food-web diversity. Quick adaptation of benthic food-web structure to seasonal variations in OM properties and its modification by local conditions may indicate high plasticity of species feeding behavior that suggests a high capacity of benthic communities to mitigate ongoing changes in the marine environment, at least within the range observed today. Our results confirm that combination of spatial and temporal scales in sampling of the food-web structure is a good indicator of the ecosystem stability and function.
Display omitted
•In fjords benthos utilized a wide range of organic matter sources.•Arctic fjord and shelf benthos displayed a high degree of omnivory.•Feeding on higher trophic levels dominated in ...deep-sea benthos.•Macrofauna mainly relied on fresher organic matter arriving to the sea floor.•Meiofauna mainly relied on the reworked organic matter from the sediments.
The knowledge on benthic trophic relations is particularly important for understanding the functioning of still pristine and less studied Arctic Ocean ecosystems. This study examines the benthic food-web structure in the European sector of the Arctic Ocean and assesses if and how it differs along depth gradients in the marginal sea-ice zone during spring. Samples of the sediment organic matter were collected in May/June 2015 and May 2016 at stations representing different sedimentary habitats (fjord, shelf, slope/basin), and stable isotopes of δ13C and δ15N were used to determine macro- and meiofauna food-web structure. Our results show that the food-web structure differed both among the three studied habitat types and between macro- and meiofauna components of benthic communities, and that these differences were related to the quality and quantity of organic matter. Meiofauna in fjords and on the shelf mainly relied on the reworked sediment organic matter while macrofauna utilized more fresh organic matter, sedimenting to the sea floor. In fjords and on the shelf, benthos displayed a high degree of omnivory and non-selective feeding while on the slope and in deep basins feeding on higher trophic levels dominated. In the latter, benthos seemed also to have utilized highly reworked organic matter. As the organic matter quantity and quality were major drivers of trophic relations in all studied areas, the benthic food webs will likely face cascading effects following the modification of pelagic food webs due to climatic changes.
Mesozooplankton research in high latitude ecosystems tends to focus on different life stages of Calanus spp. due to its biomass dominance and trophic roles. However, a complex seasonal succession of ...abundant smaller mesozooplankton taxa suggests that the ecological functioning of the mesozooplankton communities is more complicated. We studied the year‐round taxon‐specific biomass measurements and size distributions of mesozooplankton on a sub‐Arctic continental shelf based on formalin preserved samples. Our results confirm that Calanus spp. dominate the mesozooplankton biomass (81%). We show that commonly used length–weight relationships underestimate Calanus biomass in autumn and winter, and accordingly, a strong seasonal bias was introduced in our understanding of sub‐Arctic plankton communities. We observed two periods with considerable contribution of meroplankton, the planktonic larvae of benthic invertebrates, to the mesozooplankton biomass: (a) Cirripedia nauplii accounted for 17% of total biomass close to the coast in early April and (b) meroplankton comprised up to 12.7% of total biomass in late July. Based on these results, we suggest that meroplankton may play an ecologically important role in addition to their role in dispersal of benthic species. We conclude that the seasonal succession of the biomass of small‐sized holoplankton and meroplankton, often obscured by patterns in the Calanus biomass, should receive more attention as these smaller individuals are likely an important functional component of the pelagic food web.
Mesozooplankton play a key role as the major trophic link between the pelagic primary producers and higher trophic levels. Here, we show that meroplankton, the planktonic larvae of benthic invertebrates, contribute considerably to the biomass of the smallest mesozooplankton size fraction (<1 mm) during spring, the period of first feeding for most major fish stocks spawning in the sub‐Arctic. We suggest that meroplankton plays an ecologically important role, contributing to early feeding of commercial fish species.
Spatial patterns in sub-Arctic benthos Silberberger, Marc J.; Renaud, Paul E.; Buhl-Mortensen, Lene ...
Ecological monographs,
02/2019, Letnik:
89, Številka:
1
Journal Article
Recenzirano
Odprti dostop
An important goal for ecosystem-based management is to protect marine habitats and their associated fauna. Understanding the spatial structure and interrelationships of benthic communities and their ...underlying environmental drivers, therefore, is of great importance. The benthic community off the sub-Arctic Lofoten-Vesterålen islands was studied on multiple spatial scales, using the MEM (Moran's eigenvector maps) framework to identify spatial structure in broadscale (hundreds of kilometers), mesoscale (20 km), and fine-scale (1.5 km) epifaunal and infaunal communities. A combination of eigenvector-based multivariate analyses and variation partitioning on multiple sets of explanatory variables was used to identify characteristic species and environmental drivers that have a high importance in structuring the communities. Community structure of both epifauna and infauna strongly reflected the boundary of warm Atlantic (>0.5°C) and cold Arctic water masses (<0.5°C), which coincides approximately with the 800-m isobath in this region. Apart from this dominant broadscale determinant, epifauna and infauna displayed different spatial patterns and drivers. Both components differ significantly across local marine landscapes; however, this characterization is not sufficient for infauna, where additional sediment characteristics play an important role in structuring the community across all spatial scales. Within marine landscapes (mesoscale), epifauna displays a spatial structure that, for the most part, could not be attributed to any of the included environmental drivers. The case of the Lofoten-Vesterålen region demonstrated that the used analysis is a valuable tool in spatial planning, as it allows for comparison of the relative importance of individual environmental drivers for the studied faunal components, without losing the information about spatial patterns associated with individual drivers.
Studies of trophic interactions give valuable insights into the functioning of ecosystems and can be used to identify qualitative differences among ecosystems. Here, we use natural stable isotope ...concentrations (δ13C and δ15N) to study the food-web structure in four contrasting locations on the northern European continental shelf: two sub-Arctic locations in the Lofoten-Vesterålen region (fjord vs. open shelf) and two temperate locations (northern vs. southern North Sea). Phytoplankton was identified as the major primary producer in all studied ecosystems, even in the sub-Arctic fjord, where macroalgae only played a minor role in the food web. We used mixing models to determine the relative reliance on prey of benthic affinity and found that reliance on benthic prey was higher in the North Sea than in the Lofoten-Vesterålen region. Atlantic cod (Gadus morhua) was identified as the single top-predator in the North Sea, utilizing food from both, benthic and pelagic trophic channels. More separate benthic and pelagic trophic channels characterize the Lofoten-Vesterålen region, where G. morhua acts as part of the pelagic food chain. Furthermore, our data indicate that the recent mesopredator outburst in the southern North Sea might have been enhanced by reduced predation pressure due to the collapse of the local cod stocks. We conclude that the resilience towards a high fishing pressure is higher in the Lofoten-Vesterålen region than in the North Sea.
Stable isotope analysis has become one of the most widely used techniques in ecological studies. However, there are still uncertainties about the effects of sample preservation and pre-treatment on ...the ecological interpretation of stable isotope data and especially on Bayesian stable isotope mixing models. Here, Bayesian mixing models were used to study how three different preservation methods (drying, freezing, formalin) and two pre-treatments (acidification, lipid removal) affect the estimation of the utilized organic matter sources for two benthic invertebrate species (
Limecola balthica
,
Crangon crangon
) collected in the Baltic Sea. Furthermore, commonly used mathematical lipid normalization and formalin correction were applied to check if they were able to adjust the model results correctly. Preservation effects were strong on model outcomes for frozen as well as formalin preserved
L. balthica
samples, but not for
C. crangon
. Pre-treatment effects varied with species and preservation method and neither lipid normalization nor mathematical formalin correction consistently resulted in the desired model outcomes. Our analysis highlights that particularly small, not significant changes in stable isotope ratios introduced by different preservation and pre-treatments display a so far unrecognized source of error in stable isotope mixing models. We conclude that mathematical correction of benthic invertebrate stable isotopes data should be avoided for Bayesian mixing models and that previously unaddressed effects of sample preservation (especially those arising from preservation by freezing) have potentially biased our understanding of the utilization of organic matter in aquatic food webs.
PDF
