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Response of coccolithophore communities to oceanographic and atmospheric processes across the North- and Equatorial Atlantic
Get PDFChanges in coccolithophore productivity in response to climate-driven ocean warming are likely to have cascading biogeochemical effects that feed back to the changing climate. This paper investigates the role (and interplay) of large-scale oceanographic and atmospheric processes across the North- and Equatorial Atlantic, including Saharan dust deposition, on the distribution of coccolithophore communities. The study is based on biological and hydrological data collected across the photic zone of the ocean, and aerosol data collected from the lower atmosphere, across 50°N–1°S during the Atlantic Meridional Transect in boreal Autumn of 2018 (AMT28), in synergy with Earth Observations. Results confirm existing understanding of the distribution of coccolithophore communities which are related to major meridional hydrological gradients across the North Atlantic. Dynamic, oxygenated and microphytoplankton-enriched waters at higher-latitudes were characterized by less diverse coccolithophore populations, dominated by placolith-bearing r-selected coccolithophores. In contrast, the heavily stratified and picoplankton-enriched waters of the subtropical gyre revealed more diverse populations, dominated by umbelliform coccolithophores and holococcolithophores at the surface, and by floriform taxa in the lower photic zone. Mean concentrations of 14.4×103 cells/L present in the North Atlantic Tropical Gyre Province (30–12°N), only slightly lower compared to 17.7×103 cells/L produced in the North Atlantic Drift province (50–40°N), provide a snapshot perspective on the importance of coccolithophore production in heavily stratified gyre conditions. Higher concentrations of 19’-Hexanoyloxyfucoxanthin (HexFuco) in regions of enhanced production of r-selected placolith-bearing species suggest that this pigment should not be generalized as a proxy for the entire coccolithophore community. Enhanced abundances of fast-blooming Emiliania huxleyi and Gephyrocapsa oceanica, and of cyanobacteria (including both picoplankton and N2-fixing Trichodesmium spp.) at the surface of the region of more persistent Saharan dust deposition (at ~12-10°N) appeared to result from dust-born nutrient input. Underneath this stratified surface layer, enhanced productivity in the deep chlorophyll maximum (DCM) appeared decoupled from that on the surface, fueled by geostrophic eastward shoaling of the nutricline across the tropical North Atlantic. As this was the region of highest macronutrient concentrations measured along and below the nutricline, our data suggest that the NE tropical Atlantic may act as a permanent dust-born nutrient depocenter as previously hypothesized
Anthropogenic nitrogen pollution threats and challenges to the health of South Asian coral reefs
Get PDFNitrogen pollution is a widespread and growing problem in the coastal waters of South Asia yet the ecological impacts on the region’s coral ecosystems are currently poorly known and understood. South Asia hosts just under 7% of global
coral reef coverage but has experienced significant and widespread coral loss in recent decades. The extent to which this coral ecosystem decline at the regional scale can be attributed to the multiple threats posed by nitrogen pollution has been largely overlooked in the literature. Here, we assess the evidence for nitrogen pollution impacts on corals in the central Indian Ocean waters of
India, Sri Lanka and the Maldives. We find that there is currently limited evidence with which to clearly demonstrate widespread impacts on coral reefs from nitrogen pollution, including from its interactions with other stressors such
as seawater warming. However, this does not prove there are no significant impacts, but rather it reflects the paucity of appropriate observations and related understanding of the range of potential impacts of nitrogen pollution at
individual, species and ecosystem levels. This situation presents significant research, management and conservation challenges given the wide acceptance that such pollution is problematic. Following from this, we recommend more systematic collection and sharing of robust observations,
modelling and experimentation to provide the baseline on which to base prescient pollution control action
Monitoring and modelling marine zooplankton in a changing climate
Get PDFZooplankton are major consumers of phytoplankton primary production in marine ecosystems. As such, they represent a critical link for energy and matter transfer between phytoplankton and bacterioplankton to higher trophic levels and play an important role in global biogeochemical cycles. In this Review, we discuss key responses of zooplankton to ocean warming, including shifts in phenology, range, and body size, and assess the implications to the biological carbon pump and interactions with higher trophic levels. Our synthesis highlights key knowledge gaps and geographic gaps in monitoring coverage that need to be urgently addressed. We also discuss an integrated sampling approach that combines traditional and novel techniques to improve zooplankton observation for the benefit of monitoring zooplankton populations and modelling future scenarios under global changes
Mesoscale Eddies Enhance the Air‐Sea CO 2 Sink in the South Atlantic Ocean
Get PDFMesoscale eddies are abundant in the global oceans and known to affect oceanic and atmospheric
conditions. Understanding their cumulative impact on the air-sea carbon dioxide (CO2) flux may have
significant implications for the ocean carbon sink. Observations and Lagrangian tracking were used to estimate
the air-sea CO2 flux of 67 long lived (>1 year) mesoscale eddies in the South Atlantic Ocean over a 16 year
period. Both anticyclonic eddies originating from the Agulhas retroflection and cyclonic eddies originating
from the Benguela upwelling act as net CO2 sinks over their lifetimes. Anticyclonic eddies displayed an
exponential decrease in the net CO2 sink, whereas cyclonic eddies showed a linear increase. Combined, these
eddies significantly enhanced the CO2 sink into the South Atlantic Ocean by 0.08 ± 0.04%. The studied eddies
constitute a fraction of global eddies, and eddy activity is increasing; therefore, explicitly resolving eddies
appears critical when assessing the ocean carbon sink
Stakeholder insights into embedding marine net gain for offshore wind farm planning and delivery
Get PDFThe rapid expansion of offshore wind farms plays a key role in meeting global Net Zero targets by 2050 and if
delivered sustainably could address the dual challenges of climate change and biodiversity loss. Many countries
are embracing ambitious approaches to environmental impact reduction by implementing concepts such as Biodiversity Net Gain, Nature Positive and No Net Loss. Such policies are now recognized in European and UK legislation, although generally only applicable to terrestrial activities. For the marine realm, there is little consensus on how Marine Net Gain can provide optimal environmental and societal outcomes from marine activities such as offshore wind farm construction, operation and decommissioning. This study sought to clarify the key issues that need to be addressed for effective implementation of Marine Net Gain. Following recruitment through a stakeholder mapping exercise, in-workshop and follow-up questionnaires sought to elicit expert opinions from multi-sector UK offshore wind farm stakeholders on a range of aspects of Marine Net Gain policy
formulation and delivery. Over 80 % of participants indicated that certain external inputs, including information
for climate change adaptation options and habitat mapping data, were important to enable delivery of Marine
Net Gain. The most important ecosystem services to include within Net Gain measures were perceived as those
relating to fisheries (mean 4.50, SD 0.51), maintaining nursery habitats (mean 4.41, SD 0.59), and climate
regulation (mean 4.20, SD 1.). Stakeholders felt the most important Net Gain actions for environmental restoration/enhancement for future offshore wind deployment were shellfish/mussel bed (ave rank score 4.06) and
invertebrate habitat restoration (ave rank score 4.60), and actions supporting plankton communities (ave rank
score 4.67). Stakeholders agreed (83 %) that Net Gain actions should be considered at the decommissioning
stage, and the preferred decommissioning option was the complete removal or abandonment of all structures.
Stakeholders felt that strategic Net Gain assessments should prioritize fishing pressures (dredging: mean 4.27, SD
1.03; line and net: mean 4.21, SD 0.89) and those arising from physical structures (mean 4.0, SD 0.85). Aquaculture farming was deemed most feasible to co-exist with fixed offshore wind farms (means 3.93–4.19), while
floating wind farms were felt to be more co-locatable with fishing practices (means 3.94–4.06) and carbon
capture storage devices (mean 3.87) compared to fixed structures. Recommendations are suggested for future
policy development and scientific research in relation to the application of Marine Net Gain assessment for
offshore wind farm projects
Development and diversity of epibiont assemblages on cultivated sugar kelp (Saccharina latissima) in relation to farming schedules and harvesting techniques
No full textSeaweed farming in Europe is growing and may provide environmental benefits, including habitat provisioning, coastal protection, and bioremediation. Habitat provisioning by seaweed farms remains largely unquantified, with previous research focused primarily on the detrimental effects of epibionts, rather than their roles in ecological functioning and ecosystem service provision. We monitored the development and diversity of epibiont assemblages on cultivated sugar kelp (Saccharina latissima) at a farm in Cornwall, southwest UK, and compared the effects of different harvesting techniques on epibiont assemblage structure. Increases in epibiont abundance (PERMANOVA, F4,25 = 100.56, p 6000 individuals per kelp plant with a taxonomic richness of ~9 phyla per kelp by late summer (August). Assemblages were dominated by crustaceans (mainly amphipods), molluscs (principally bivalves) and bryozoans, which provide important ecological roles, despite reducing crop quality. Partial harvesting techniques maintained, or increased, epibiont abundance and diversity beyond the farming season; however, these kelp plants were significantly fouled and would not be commercially viable in most markets. This paper improves understanding of epibiont assemblage development at European kelp farms, which can inform sustainable, ecosystem-based approaches to aquaculture
Trait trade-offs in phagotrophic microalgae: the mixoplankton conundrum
Get PDFAnalysis of trait trade-offs, through which physiological traits requiring common resources are ‘traded’ to optimize competitive advantage, provides a route to simplify and more readily understand the complexities of ecology. The concept of trait trade-offs has found favour in plankton research, especially directed at phytoplankton, defined here as phototrophs incapable of phagotrophy. Mixoplankton, defined as protists that combine phototrophy and phagotrophy, are now recognized as being widespread and significant members of the protist plankton community; many photoflagellate ‘phytoplankton’ are actually mixoplankton, as are many ‘(microbial) zooplankton’. Mixoplankton might be expected to be dominant, being able to exploit different trophic strategies while simultaneously eliminating competitors. That mixoplankton are not dominant suggests that physiological trait trade-offs erode their apparent competitive edge. We present a systematic analysis of potential trait trade-offs in phototrophic protists focused on mixoplankton. We find no clear evidence to support trait trade-off arguments in plankton research, except perhaps for acquired phototrophy in mixoplanktonic ciliates versus zooplanktonic ciliates. Our findings suggest that the presence of various mixoplankton throughout the surface ocean waters is most likely explained by factors other than trait trade-offs. Diversities in mixoplankton form and function thus reflect that evolution of these organisms from very different lineages, provide them with advantages to function competitively in mature ecosystems with complex trophic interplay. Indeed, the complexity of those lineages is inconsistent with core trait trade-off definitions; there is no single ancestral mixoplankton nor a common environment supporting trait-trade-off-directed evolutio
Plastitar in the Mediterranean Sea: New records and the first geochemical characterization of these novel formations
Get PDFA new geological formation consisting of plastic debris admixed to petroleum oil residue, termed “plastitar”, has been recently described in the Canary Islands. Here, we report its widespread occurrence across the Mediterranean coast and new insights into its biogeochemical composition. Specifically, we found marked differences in the diagenetic stable indicator profiles, suggesting a heterogeneous seeps provenance. Moreover, the 801 plastic particles found in the 1372 g of tar surveyed, with a maximum concentration of 2.0 items/g, showed interesting patterns in the tar mat, with nurdles predominantly layered in the external of the tar mat and lines in the inner core. Overall, the collected observation suggests that tar entraps plastics through a stepwise process and is a sink for them
How environmental drivers of spatial synchrony interact
Get PDFSpatial synchrony, the tendency for populations across space to show correlated fluctuations, is a fundamental feature of population dynamics, linked to central topics of ecology such as population cycling, extinction risk, and ecosystem stability. A common mechanism of spatial synchrony is the Moran effect, whereby spatially synchronized environmental signals drive population dynamics and hence induce population synchrony. After reviewing recent progress in understanding Moran effects, we here elaborate a general theory of how Moran effects of different environmental drivers acting on the same populations can interact, either synergistically or destructively, to produce either substantially more or markedly less population synchrony than would otherwise occur. We provide intuition for how this newly recognized mechanism works through theoretical case studies and application of our theory to California populations of giant kelp. We argue that Moran interactions should be common. Our theory and analysis explain an important new aspect of a fundamental feature of spatiotemporal population dynamics
At what scale should we assess the health of pelagic habitats? Trade-offs between small-scale manageable pressures and the need for regional upscaling
Get PDFMajor planktonic lifeforms such as diatoms, dinoflagellates, meroplankton and holoplankton have recently shown significant and alarming changes in abundance - mainly downwards trends - around the northwest European shelf. This has major implications for food web connections and for ecosystem services including seafood provision and carbon storage. We have quantified these changes in abundance for 2006–2019/20 using a Plankton Index (PI) and show that the scale of spatial aggregation is critical to the ability of the PI to detect change, understand causal mechanisms, and provide advice to policymakers.
We derived PI statistics in the Celtic and North Seas from data from the Continuous Plankton Recorder survey offshore and England’s Environment Agency inshore using three sets of spatial units: (i) Ecohydrodynamic (EHD) units based on hydro-biogeochemical modelling, (ii) ‘COMP4′ areas based on cluster analysis of satellite data for chlorophyll a and primary productivity, and (iii) English coastal and estuarine Water Framework Directive (WFD) waterbodies. For the largest scale areas, the EHD units (median size 87,000 km2), we find greater change in plankton communities than previously reported, suggesting that these shifts have continued and possibly intensified in recent years. The smaller-scale COMP4 areas (median size 6,700 km2) appear to encompass more spatially coherent changes in plankton community structure than EHD units; at this scale PI values indicate community shifts of greater magnitude. These COMP4 areas provide a reasonable compromise scale for linking offshore plankton communities to large-scale drivers of change such as climate warming. For inshore plankton communities, larger changes are detected at the smaller WFD waterbody scale (median size 11 km2). This scale allows direct links to coastal management measures and is more suitable for linking to land-sourced pressures.
Recent integration of the UK’s OSPAR and WFD plankton monitoring data management enables the exploration of changes across spatial scales to develop a holistic understanding of ecosystem health. Regional-sea scale derivation of the PI for coastal waters provides a clear indication that changes are occurring, at least in phytoplankton communities, while localised PI statistics offer an additional layer of information which can be an important tool for linking to localised drivers of change including coastal anthropogenic pressures. Broadscale inshore zooplankton monitoring is needed to evaluate the coastal plankton community holistically; zooplankton communities offshore are also changing but these changes cannot currently be linked to coastal processes. Layering information across spatial scales provides a breadth of system-level understanding beyond what any one typology can provide