Mud worm stirs up contaminants taken up by perch and eel pout

Perch. Illustration: Camilla Bolner/Azote

Ever since the turn of the millennium seven years followed both perch and eelpout showed an increase in a biomarker for them trying to detox, called EROD activity. The scientist in this study tried to find out why they were under stress and unravelled that it was linked to a sudden rise in numbers of an invasive polychaete mud worm Marenzelleria spp that stirred up toxic Polyaromatic hydrocarbons (PAHs) coming from diesel and combustions. The contaminants were then freed from the sediment into the water, exposing both fish.

Eelpout. Illustration: Camilla Bolner/Azote

Adding to the misery, perch contained a higher mercury concentration over time as well, and this was linked to a change in feeding pattern – based on stable isotope diet tracers they seem to eat more Saduria, a predatory bottom living isopod. The good news is that eelpout, conversely, decreased its mercury concentration over time because they eat more on other food sources instead.

Read the full paper here: Ecological changes as a plausible explanation for differences in uptake of contaminants between European perch and eelpout in a coastal area of the Baltic Sea

Three facts about perch and eelpout

  • Perch can become up to 20 years old
  • Eelpout is that they give birth to living offspring, which kind of rare among fish species
  • Eelpouts have a green skeleton!

Source: Livet i havet 

Organisms in the bottom of the Baltic ditch cyanobacteria from the summer blooms

The clam Limecola balthica, the amphipod Monoporeia affinis, the polychaete Marenzelleria sp. Illustration: Per Hedberg.

Another study showed the food preferences for the organisms the deepest down in the Baltic a clam, an amphipod and a polychaete which are important as oxygenators of soft bottoms and as prey for, for example juvenile cod, gobies and flat fish. The study showed that all of the animals preferred to eat the diatoms from the spring blooms and were not so interested to eat the cyanobacteria from the summer blooms. The reason that they like the diatoms so much might be that they are rich in “good” fatty acids, namely the essential ones, which they need to be healthy. When they lack the “good” fatty acids, they can stunt in growth, fail to reproduce or produce malformed eggs or embryos.

However, climate change and a warmer climate will most likely shift so that there are instead increased summer cyanobacterial blooms, and thus food that these important animals don’t like. And if they start eating less of these cyanobacteria, they will sediment down to the bottom and consumed by bacteria. The downside, is that this process consumes a lot of oxygen making the bottom hard to inhabit for the species in the study - they need oxygen. This could be a double blow to the organisms in the bottom of the Baltic Sea – they both starve and suffocate. To maintain the production in the Baltic Sea we need to maintain the phytoplankton composition as it is today serving the animals in the bottom of the Baltic Sea the food they prefer.

Read the full paper here:Effects of changing phytoplankton species composition on carbon and nitrogen uptake in benthic invertebrates

Three facts about the organisms in the bottom of the Baltic

  • The Baltic Sea Clam Limecola balthica is burrowed in the soft sediment and for it to be able to breath they have two long breathing tubes up to six times bigger than the clam itself that reach the water over the sediment.
  • The amphipod Monoporeia affinis can be burrowed in the soft sediment only one meter below up to 70 meters below
  • The polychaete Marenzelleria sp. moves around with a corkscrew movement

Source: Livet i havet 

Seagrass meadows in rough weather are better carbon sinks

Researcher collecting a 2 m long sediment core in an eelgrass meadow on the Swedish west coast. The sediment will be used for analyzing carbon accumulation rates and seagrass sediment thickness to better understand how these meadows function as carbon sinks. Photo: Maria Asplund

In Sweden for example we have seagrass meadows, accustomed to the cold weather here up in the north called eelgrass (Zostera marina). The study analyzing 53 seagrass sites found that the meadows exposed to more wind and waves by the open ocean have higher carbon stocks likely because the more exposed meadows have a more compacted sediment, which increases the carbon density, compared to more muddy sediment bed types you can find mostly in more sheltered embayments protected from wind and waves.

If we get more storms due to climate change, the meadows already exposed to more wind and waves now will potentially be more resilient as heavier sediment is not as easily eroded. These meadows might therefore be even more important as carbon sinks in the future.

The blue carbon literature has increased substantially the last 5-6 years, which have improved our understanding on the carbon sequestration processes in these environments. A lot of the older data are based on a relatively few study areas with unusually high carbon accumulation, and it might therefore be that the seagrass carbon storage capacity has been overestimated. What one could wish for is a new global review evaluating the last 8-10 years of data to get a better picture of the carbon sink capacity in seagrass meadows.

Read the full paper here: The influence of hydrodynamic exposure on carbon storage and nutrient retention in eelgrass (Zostera marina L.) meadows on the Swedish Skagerrak coast

Three facts about eelgrass

  • Eelgrass have leaves 30-60 cm long, but can become up to 1,5 meters
  • Eelgrass meadows reproduce vegetatively
  • A big eelgrass meadow can consist of one single individual and can be many hundred years old

Source: Livet i havet