New research paper on overwintering zooplankton in the North Sea

New open access paper published in Progress in Oceanography Overwintering distribution, inflow patterns and sustainability of Calanus finmarchicus in the North Sea.

The modelled abundance (1000 individual/m2) of overwintering C. finmarchicus in the North Sea

Some of the highlights include:

•High overwintering biomass in Norwegian Trench and north-west North Sea shelf.

•Inflow accounts for 41% of North Sea biomass and drives interannual variability.

•Norwegian Trench and East Shetland Atlantic Inflow are important inflow pathways.

C. finmarchicus in the North Sea is not self-sustained but dependent on the inflow.

•Biomass carried by East Shetland Atlantic Inflow decreases over 2000–2016.

Abstract: Calanoid copepods are key taxa in the North Sea as they are the main food source for many fish stocks, such as herring, mackerel and cod. In this study we use an individual-based model for Calanus finmarchicus embedded in the NORWegian ECOlogical Model system (NORWECOM) to investigate important population parameters such as biomass and abundance, distribution and interannual variability of the overwintering population, as well as the inflow of C. finmarchicus into the North Sea from adjacent areas for the 2000–2016 period. The modelled spatial–temporal patterns of C. finmarchicus abundance is comparable with the Continuous Plankton Recorder (CPR) Survey data in the northern North Sea. The simulated annual mean biomass of C. finmarchicus amounts to 0.94 million-tonnes of carbon. High overwintering biomass appears in the Norwegian Trench as well as in the north-west shelf region of the North Sea. A decreasing trend in the overwintering biomass has been detected on the path of the East Shetland Atlantic Inflow (ESAI) over the simulated period. The inflow of C. finmarchicus biomass into the North Sea from the north constitutes on average 41% of the annual mean biomass in the North Sea during the simulated 17 years, and thus determines the interannual variability of the biomass. We conclude that the C. finmarchicus population in the North Sea is not self-sustained and is highly dependent on the inflow of C. finmarchicus from the Faroe-Shetland Channel and south of the Norwegian Sea. C. finmarchicus enter the North Sea via three branches of the North Atlantic current with variable depths depending on seasons and topography. Beside the western flank of the Norwegian Trench (carrying 57% of the inflow biomass), we suggest that the ESAI is also an important agent carrying 37% of the total C. finmarchicus inflow biomass through the shelf area into the north-west of the North Sea. The annual mean outflow biomass is larger than the inflow biomass (0.52 versus 0.39 million-tonnes carbon per year), which indicates that the North Sea serves as a feeding ground and growth region for C. finmarchicus. This study is a first step towards a better understanding and quantification of the exchange of C. finmarchicus between the open seas, coastal waters and the fjords.

Get the open access paper here:

Scientists complete largest global assessment of ocean warming impacts

A group of international marine scientists has compiled the most comprehensive assessment of how ocean warming is affecting the mix of species in our oceans – and explained how some marine species manage to keep their cool.

Martin Edwards from the University of Plymouth along with other researchers from the UK, Japan, Australia, USA, Germany, Canada, South Africa and New Zealand analysed three million records of thousands of species from 200 ecological communities across the globe.

Reviewing data from 1985 – 2014, the team led by Michael Burrows of the Scottish Association for Marine Science (SAMS) in Oban showed how subtle changes in the movement of species that prefer cold-water or warm-water, in response to rising temperatures, made a big impact on the global picture. The findings, published in the journal Nature Climate Change [https://www.nature.com/articles/s41558-019-0631-5], show how warm-water species increase and cold-water marine species become less successful as the global temperature rises. However, the study also suggests that some cold-water species, and fish in particular, will continue to thrive by seeking refuge in cooler, deeper water.

Prof Burrows  further added:

“For the period from 1985 – 2014 we created the equivalent of an electoral poll in the ocean, showing swings between types of fish and plankton normally associated with either cold or warm habitats. As species increase in number and move into, or decline and leave, a particular ecological community, the make-up of that community will change in a predictable way. While this may not sound like a big change, it has a considerable impact on species that may already be on, or close to, their maximum temperature tolerance. A gradual temperature change like the one we are witnessing is not going to cause extinctions overnight but it is affecting the success of many species, not least zooplankton such as copepods, which are crucial to the ocean food web”.

Prof Edwards said the truly global study looked at data from the North Atlantic, Western Europe, Newfoundland and the Labrador Sea, east coast USA, the Gulf of Mexico, and the North Pacific from California to Alaska. While the global warming trend was widely seen, the North Atlantic showed the largest rise in average temperature during the time period. This area of the North Atlantic is routinely monitored by one of the world’s largest and longest marine biological surveys known as the Continuous Plankton Recorder (CPR) Survey which provided some key observational data in the global study. The changes observed have been driven by a seemingly small but ecologically significant rise in temperature of almost one degree Celsius in some parts of the ocean since 1985, a rapid change in just three decades. These changes are having huge implications for the abundance and distribution of plankton in our oceans.



Climate-related changes in fish and plankton communities shown by changes in Community Temperature Index values from 1985 to 2015.

New open access research paper on plankton biogeography in the North Atlantic

New research paper: Plankton biogeography in the North Atlantic Ocean and its adjacent seas: Species assemblages and environmental signatures

Loïck Kléparski, Grégory Beaugrand and Martin Edwards

Ecology and Evolution 2021; 00:1-15. DOI: 10.1002/ece3.7406

Plankton biodiversity is a key component of marine pelagic ecosystems. They are at the base of the food web, control the productivity of marine ecosystems, and provide many provisioning and regulating ecological services. It is therefore important to understand how plankton are organized in both space and time.

Abstract:

Here, we use data of varying taxonomic resolution, collected by the Continuous Plankton Recorder (CPR) survey, to map phytoplankton and zooplankton biodiversity in the North Atlantic and its adjacent seas. We then decompose biodiversity into 24 species assemblages and investigate their spatial distribution using ecological units and ecoregions recently proposed. Finally, we propose a descriptive method, which we call the environmental chromatogram, to characterize the environmental signature of each plankton assemblage. The method is based on a graphic that identifies where species of an assemblage aggregate along an environmental gradient composed of multiple ecological dimensions. The decomposition of the biodiversity into species assemblages allows us to show (a) that most marine regions of the North Atlantic are composed of coenoclines (i.e., gradients of biocoenoses or communities) and (b) that the overlapping spatial distribution of assemblages is the result of their environmental signatures. It follows that neither the ecoregions nor the ecological units identified in the North Atlantic are characterized by a unique assemblage but instead by a mosaic of assemblages that overlap in many places.

Spatial distribution of total
plankton taxonomic richness in the North Atlantic

Get the open access paper here: https://onlinelibrary.wiley.com/doi/10.1002/ece3.7406

Warming drives ‘fundamental’ changes to ocean.

Climate change has wrought major changes to ocean stability faster than previously thought, according to a recent study, raising alarms over its role as a global thermostat and the marine life it supports.

The research published in the journal Nature looked at 50 years of data and followed the way in which surface water “decouples” from the deeper ocean.

Climate change has disrupted ocean mixing, a process that helps store away most of the world’s excess heat and a significant proportion of CO2.

Water on the surface is warmer — and therefore less dense — than the water below, a contrast that is intensified by climate change.

Global warming is also causing massive amounts of fresh water to flush into the seas from melting ice sheets and glaciers, lowering the salinity of the upper layer and further reducing its density.

This increasing contrast between the density of the ocean layers makes mixing harder, so oxygen, heat and carbon are all less able to penetrate to the deep seas.

Long-term responses of North Atlantic calcifying plankton to climate change

Study on calcifying plankton and climate change published in Nature Climate Change

Abstract:

The global increase in atmospheric carbon dioxide concentration is potentially threatening marine biodiversity in two ways. First, carbon dioxide and other greenhouse gases accumulating in the atmosphere are causing global warming. Second, carbon dioxide is altering sea water chemistry, making the ocean more acidic.

Although temperature has a cardinal influence on all biological processes from the molecular to the ecosystem level, acidification might impair the process of calcification or exacerbate dissolution of calcifying organisms.

Here, we show however that North Atlantic calcifying plankton primarily responded to climate-induced changes in temperatures during the period 1960–2009, overriding the signal from the effects of ocean acidification. We provide evidence that foraminifers, coccolithophores, both pteropod and non-pteropod molluscs and echinoderms exhibited an abrupt shift circa 1996 at a time of a substantial increase in temperature and that some taxa exhibited a poleward movement in agreement with expected biogeographical changes under sea temperature warming. Although acidification may become a serious threat to marine calcifying organisms, our results suggest that over the study period the primary driver of North Atlantic calcifying plankton was oceanic temperature.

more information: https://www.nature.com/articles/nclimate1753