8604 research outputs found
Sort by
Marine heatwave duration and intensity interact to reduce physiological tipping points of kelp species with contrasting thermal affinities
No full textBackground and Aims
Marine heatwaves (MHWs) are widely recognized as pervasive drivers of ecosystem change, yet our understanding of how different MHW properties mediate ecological responses remains largely unexplored. Understanding MHW impacts on foundation species is particularly important, given their structural role in communities and ecosystems.
Methods
We simulated a series of realistic MHWs with different levels of intensity (Control: 14 °C, Moderate: 18 °C, Extreme: 22 °C) and duration (14 or 28 d) and examined responses of two habitat-forming kelp species in the southwest UK. Here, Laminaria digitata reaches its trailing edge and is undergoing a range contraction, whereas Laminaria ochroleuca reaches its leading edge and is undergoing a range expansion.
Key Results
For both species, sub-lethal stress responses induced by moderate-intensity MHWs were exacerbated by longer duration. Extreme-intensity MHWs caused dramatic declines in growth and photosynthetic performance, and elevated bleaching, which were again exacerbated by longer MHW duration. Stress responses were most pronounced in L. ochroleuca, where almost complete tissue necrosis was observed by the end of the long-duration MHW. This was unexpected given the greater thermal safety margins assumed with leading edge populations. It is likely that prolonged exposure to sub-lethal thermal stress exceeded a physiological tipping point for L. ochroleuca, presumably due to depletion of internal reserves.
Conclusions
Overall, our study showed that exposure to MHW profiles projected to occur in the region in the coming decades can have significant deleterious effects on foundation kelp species, regardless of their thermal affinities and location within respective latitudinal ranges, which would probably have consequences for entire communities and ecosystems
Home sweet home: Comparison of epibiont assemblages associated with cultivated and wild sugar kelp (Saccharina latissima), co-cultivated blue mussels (Mytilus edulis) and farm infrastructure
No full textSeaweed farming is expanding in Europe and may provide environmental benefits similar to those from natural kelp forests and shellfish farms, including habitat provisioning. Few studies have substantiated these claims however, and it remains uncertain whether seaweed farms will support similar biodiversity to kelp forests or provide valuable long-term habitat beyond the harvest season. We repeatedly surveyed an integrated sugar kelp (Saccharina latissima) and blue mussel (Mytilus edulis) farm in southwest UK to compare epibiont assemblages between cultivated kelps, to those from three nearby wild kelp populations, and to epibionts on farmed mussel lines and unseeded ‘bare’ lines. We found farmed kelps supported over 217 times the abundance of epibionts living on wild kelps at harvest time, however, taxonomic diversity per kelp was lower at the farm. Farmed kelp assemblages were dominated by amphipods, which were present on the wild kelps but in much lower numbers. Farmed kelp also supported distinct assemblages to cultivated mussels, which were similarly dominated by amphipods, but hosted higher relative abundances of crabs, echinoderms, worms and red algal biomass. The bare lines were heavily colonised by another pseudo-kelp, Saccorhiza polyschides, which supported similar epibiont assemblages to the seeded S. latissima lines. Our findings indicate that cultivating bivalves alongside seaweed can increase habitat provisioning at a seaweed farm and extend its permanence beyond typical seaweed cultivation periods as bivalves have longer, continuous farming periods. However, the presence of mussels will likely influence the epibiont assemblages on the farmed kelp, which are distinct from wild kelp populations
Metatranscriptomics reveals diversity of symbiotic interaction and mechanisms of carbon exchange in the marine cyanolichen Lichina pygmaea
Get PDFLichens are exemplar symbioses based upon carbon exchange between photobionts and their mycobiont hosts. Historically considered a two-way relationship, some lichen symbioses have been shown to contain multiple photobiont partners; however, the way in which these photobiont communities react to environmental change is poorly understood.
Lichina pygmaea is a marine cyanolichen that inhabits rocky seashores where it is submerged in seawater during every tidal cycle. Recent work has indicated that L. pygmaea has a complex photobiont community including the cyanobionts Rivularia and Pleurocapsa. We performed rRNA-based metabarcoding and mRNA metatranscriptomics of the L. pygmaea holobiont at high and low tide to investigate community response to immersion in seawater.
Carbon exchange in L. pygmaea is a dynamic process, influenced by both tidal cycle and the biology of the individual symbiotic components. The mycobiont and two cyanobiont partners exhibit distinct transcriptional responses to seawater hydration.
Sugar-based compatible solutes produced by Rivularia and Pleurocapsa in response to seawater are a potential source of carbon to the mycobiont. We propose that extracellular processing of photobiont-derived polysaccharides is a fundamental step in carbon acquisition by L. pygmaea and is analogous to uptake of plant-derived carbon in ectomycorrhizal symbioses
The genome sequence of the greater pipefish, Syngnathus acus (Linnaeus, 1758)
No full textWe present a genome assembly from an individual Syngnathus acus (the greater pipefish; Chordata; Actinopteri; Syngnathiformes; Syngnathidae). The genome sequence is 359.2 megabases in span. Most of the assembly is scaffolded into 22 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 16.5 kilobases in lengt
Continued glacial retreat linked to changing macronutrient supply along the West Antarctic Peninsula
Get PDFAt the West Antarctic Peninsula (WAP), continued atmospheric and oceanic warming is causing significant physical and biogeochemical changes to glaciers and the marine environment. We compare sediment sources and drivers of macronutrient distributions at two bays along the WAP during austral summer 2020, using radioactive radium and stable oxygen isotopes to trace sedimentary influences and quantify different freshwater inputs. In the Ryder Bay, where the Sheldon Glacier is marine-terminating, radium activities at the sediment-water interface indicate considerable benthic mixing. Using radium isotope activity gradients to resolve radium and macronutrient fluxes, we find buoyant meltwater proximal to the glacier drives vigorous mixing of sediment and entrainment of macronutrient deep waters, on the order of 2.0 × 105 mol d− 1 for nitrate. Conversely, in the
Marian Cove, where the Fourcade Glacier terminates on land, low salinities and oxygen isotopes indicate a meltwater-rich surface layer <1 m thick and rich in sediment, and strong vertical mixing to the seafloor. A continued shift to land-terminating glaciers along the WAP may have a significant impact upon nutrient and sediment supply to the euphotic zone, with impacts upon primary productivity and carbon uptake efficiency. The future of primary production, carbon uptake, and food web dynamics is therefore linked to glacier retreat dynamics in the many fjords along the WAP
The Mixoplankton Database (MDB): Diversity of photo‐phago‐trophic plankton in form, function, and distribution across the global ocean
Get PDFProtist plankton are major members of open-water marine food webs. Traditionally divided between phototrophic phytoplankton and phagotrophic zooplankton, recent research shows many actually combine phototrophy and phagotrophy in the one cell; these protists are the “mixoplankton.” Under the mixoplankton paradigm, “phytoplankton” are incapable of phagotrophy (diatoms being exemplars), while “zooplankton” are incapable of phototrophy. This revision restructures marine food webs, from regional to global levels. Here, we present the first comprehensive database of marine mixoplankton, bringing together extant knowledge of the identity, allometry, physiology, and trophic interactivity of these organisms. This mixoplankton database (MDB) will aid researchers that confront difficulties in characterizing life traits of protist plankton, and it will benefit modelers needing to better appreciate ecology of these organisms with their complex functional and allometric predator–prey interactions. The MDB also identifies knowledge gaps, including the need to better understand, for different mixoplankton functional types, sources of nutrition (use of nitrate, prey types, and nutritional states), and to obtain vital rates (e.g. growth, photosynthesis, ingestion, factors affecting photo’ vs. phago’ - trophy). It is now possible to revisit and re-classify protistan “phytoplankton” and “zooplankton” in extant databases of plankton life forms so as to clarify their roles in marine ecosystems
Unifying biological field observations to detect and compare ocean acidification impacts across marine species and ecosystems: what to monitor and why
Get PDFAbstract. Approximately one-quarter of the CO2 emitted
to the atmosphere annually from human activities is absorbed by the ocean, resulting in a reduction of seawater
pH and shifts in seawater carbonate chemistry. This multidecadal process, termed “anthropogenic ocean acidification” (OA), has been shown to have detrimental impacts on marine ecosystems. Recent years have seen a globally coordinated effort to measure the changes in seawater chemistry caused by OA, with best practices now available for these measurements. In contrast to these substantial advances in observing physicochemical changes due to OA, quantifying their biological consequences remains challenging, especially from in situ observations under real-world conditions. Results from 2 decades of controlled laboratory experiments on OA have given insight into the likely processes and mechanisms by which elevated CO2 levels affect biological process, but the manifestation of these process across a plethora of natural situations has yet to be fully explored. This challenge requires us to identify a set of fundamental biological and ecological indicators that are (i) relevant across all marine ecosystems, (ii) have a strongly demonstrated link to OA, and (iii) have implications for ocean health and the provision of ecosystem
services with impacts on local marine management strategies and economies. This paper draws on the understanding
of biological impacts provided by the wealth of previous experiments, as well as the findings of recent meta-analyses, to propose five broad classes of biological indicators that, when coupled with environmental observations including carbonate chemistry, would allow the rate and severity of biological change in response to OA to be observed and compared. These broad indicators are applicable to different ecological systems, and the methods for data analysis suggested here would allow researchers to combine biological response data across regional and global scales by correlating rates of biological change with the rate of change in carbonate chemistry parameters. Moreover, a method using laboratory observation to design an optimal observing strategy (frequency and duration) and observe meaningful biological rates of change highlights the factors that need to be considered when applying our proposed observation strategy. This innovative observing methodology allows inclusion of a wide diversity of marine ecosystems in regional and global assessments and has the potential to increase the contribution of OA observations from countries with developing OA science capacity
Ocean circulation and biological processes drive seasonal variations of dissolved Al, Cd, Ni, Cu, and Zn on the Northeast Atlantic continental margin
Get PDFNutrients and nutrient-like dissolved trace metals (dTMs) are essential for the functioning of marine organisms
and therefore form an important part of ocean biogeochemical cycles. Here, we report on the seasonal distributions of dissolved zinc (dZn), nickel (dNi), copper (dCu), cadmium (dCd), aluminum (dAl), and nutrients on the Northeast Atlantic continental margin (Celtic Sea), which is representative for temperate shelf seas globally. Variations in surface water dTM and nutrient concentrations were mainly regulated by seasonal changes in biological processes. The stoichiometry of dTMs (especially for dCu and dZn) and nutrients on the continental shelf was additionally affected by fluvial inputs. Nutrients and dTMs at depth on the continental slope were determined by water mass mixing driven by ocean circulation, without an important role for local remineralization processes. The Mediterranean Outflow Waters are especially important for delivering Mediterranean sourced dTMs to the Northeast Atlantic Ocean and drive dTM:nutrient kinks at a depth of ~1000 m. These results highlight the importance of riverine inputs, seasonality of primary production and ocean circulation on the Distributions of nutrients and nutrient-like dTMs in temperate continental margin seas. Future climate related changes in the forcing factors may impact the availability of nutrients and dTMs to marine organisms in highly productive continental shelf regions and consequently the regional carbon cycle
Satellite-derived multivariate world-wide lake physical variable timeseries for climate studies
Get PDFA consistent dataset of lake surface water temperature, ice cover, water-leaving reflectance, water level and extent is presented. The collection constitutes the Lakes Essential Climate Variable (ECV) for inland waters. The data span combined satellite observations from 1992 to 2020 inclusive and quantifies over 2000 relatively large lakes, which represent a small fraction of the number of lakes worldwide but a significant fraction of global freshwater surface. Visible and near-infrared optical imagery, thermal imagery and microwave radar data from satellites have been exploited. All observations are provided in a common grid at 1/120° latitude-longitude resolution, jointly in daily files. The data/algorithms have been validated against in situ measurements where possible. Consistency analysis between the variables has guided the development of the joint dataset. It is the most complete collection of consistent satellite observations of the Lakes ECV currently available. Lakes are of significant interest to scientific disciplines such as hydrology, limnology, climatology, biogeochemistry and geodesy. They are a vital resource for freshwater supply, and key sentinels for global environmental change
Impacts of coral bleaching on reef fish abundance, biomass and assemblage structure at remote Aldabra Atoll, Seychelles: insights from two survey methods
Get PDFIntroduction: Coral bleaching immediately impacts the reef benthos, but effects on fish communities are less well understood because they are often delayed and confounded by anthropogenic interactions.
Methods: We assessed changes in fish abundance, biomass and community composition before and after the 2015/16 coral bleaching event at Aldabra Atoll, Seychelles, where local human impacts are minimal, but reefs suffered 50% bleaching-induced coral mortality. We monitored 12 shallow (2–5 m water depth) and nine deep (15 m water depth) permanent survey sites using two survey methods: indicator surveys recording 84 taxa over six years (pre-: 2014; post-bleaching: 2016–2019, 2021), sizing fish based on six size-class categories, and extended fish surveys recording 198 taxa over two years (pre-: 2015; post-bleaching: 2020) with size estimates to the nearest cm (excluding fish < 8 cm).
Results: During indicator surveys, mean fish abundance did not change on deep reefs. However, abundance increased by 77% on shallow reefs between 2014 and 2016, which was mainly driven by increases in herbivores and omnivores, likely as a response to elevated turf algae cover following coral mortality. Overall (and functional group-specific) indicator fish biomass did not differ between 2014 and 2016 and remained at or above pre-bleaching levels throughout 2016–2021. In contrast, extended fish surveys in 2015 and 2020 showed a 55–60% reduction in overall abundance on shallow and deep reefs, and a 69% reduction in biomass on shallow reefs, with decreases in biomass occurring in all functional groups. Biomass on deep reefs did not differ between 2015 and 2020. Multivariate analysis of both data sets revealed immediate and long-lasting differences between pre- and post-bleaching fish community compositions, driven largely by herbivorous, omnivorous and piscivorous taxa.
Discussion: Results from the indicator surveys suggest that the bleaching event had limited impact on fish abundance and biomass, while the extended surveys recorded changes in abundance and biomass which would otherwise have gone undetected. Our findings improve understanding of the shift a broad community of fish undergoes following a mass coral bleaching event and highlights the value of survey methods that include the full suite of species to detect ecological responses to environmental drivers