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Understanding the past to guide the future, a community level response to climate change in the Kattegat (Baltic Sea), 1983 to 2017

Hopkins, Stephanie (2020) BION02 20191
Degree Projects in Biology
Abstract
Climate change is greatly affecting the world’s seas in many ways, but of those particularly at risk, are inland seas such as the Baltic Sea. In spite of this though, there still remains a large gap in our understanding of how multiple stressors can change these systems over time. Therefore, as a way to assess how copepod and phytoplankton species groups are changing within the Kattegat, multidecadal time series analyses were conducted. Perspective top-down and bottom-up drivers were also investigated to explain their changes in density over time. The results of which, found overall declines for both phytoplankton and copepod groups, but not in cyanobacteria, p < 0.001. Decreases in the surface concentrations for both total phosphorous and... (More)
Climate change is greatly affecting the world’s seas in many ways, but of those particularly at risk, are inland seas such as the Baltic Sea. In spite of this though, there still remains a large gap in our understanding of how multiple stressors can change these systems over time. Therefore, as a way to assess how copepod and phytoplankton species groups are changing within the Kattegat, multidecadal time series analyses were conducted. Perspective top-down and bottom-up drivers were also investigated to explain their changes in density over time. The results of which, found overall declines for both phytoplankton and copepod groups, but not in cyanobacteria, p < 0.001. Decreases in the surface concentrations for both total phosphorous and total nitrogen, with an increase in temperature and salinity were also found, p < 0.001. Pairwise correlations were tested using spearman rank correlation analyses. Of which showed strong negative correlations between salinity and nutrient concentrations, and where temperature had mixed effects on nutrient concentrations, both sharing a positive relationship with phosphorous and a negative relationship with nitrogen. For all parameter combinations, general linear modelling was used. Final results suggested nutrient reductions as a potential factor in phytoplankton declines, while decreasing copepod densities were found to be best explained by predation components: sprat and herring. The inclusion of herring and sprat data also generated stronger model predictabilities with lower Akaike scores and higher adjusted r-squared values for both phytoplankton and copepod densities. This suggests their inclusion is vital for future modelling of planktonic communities. (Less)
Popular Abstract
Changes in the plankton salad, a recipe for the future?

Climate change is greatly affecting the worlds’ seas in many ways. But of those particularly at risk, are coastal regions such as the Kattegat. Over the past 34 years, farming, pollution and overfishing have greatly changed its structure, and in particular, its planktonic communities that serve as the foundation for marine life.

Despite this, it has remained difficult to pinpoint how these changes are affecting the system as a whole. This is much like the problem a novice chef is faced with, when he is asked to explain how ingredients are mixed, or what the resulting flavour combinations of their mixing will be, when all he’s had to work with is a poorly written recipe.

So... (More)
Changes in the plankton salad, a recipe for the future?

Climate change is greatly affecting the worlds’ seas in many ways. But of those particularly at risk, are coastal regions such as the Kattegat. Over the past 34 years, farming, pollution and overfishing have greatly changed its structure, and in particular, its planktonic communities that serve as the foundation for marine life.

Despite this, it has remained difficult to pinpoint how these changes are affecting the system as a whole. This is much like the problem a novice chef is faced with, when he is asked to explain how ingredients are mixed, or what the resulting flavour combinations of their mixing will be, when all he’s had to work with is a poorly written recipe.

So to better understand how these system changes are driving community level responses in the Kattegat, mean monthly average densities were taken for: cyanobacteria (the toxic stuff), phytoplankton (the green stuff) and copepods (the secret ingredient to a healthy fish meal) over the past 34 years. This is in addition to mean monthly average densities for two fish groups: herring and sprat, as well as: the amount of salt, ‘the cooking temperature’, light exposure and the amount of fertilizer used. Their trends are shown to the right: phytoplankton in blue: cyanobacteria in gold: copepods in orange: herring in green: and sprat in pink. Following this, ingredient pairwise combinations were investigated before later joining all the ingredients together in a final recipe for each season.

Eureka, the recipe now explained?
Strong, and at times intense, declines in phytoplankton, copepods and fertilizer were found. While simultaneously, a steady increase in the salt and ‘cooking temperature’ was evident. It appeared as though the increased salt concentration and temperature was to blame for the decreases in fertilizer and so subsequently, less green stuff grew. This lower food availability only partially explained the declines in copepods though, which like the green stuff. Instead, their subsequent decline appeared to be caused by the fish, who just were too hungry and kept eating them faster than they themselves could enjoy their salad. These fish also appeared to be eating the phytoplankton, and so did contribute in explaining their decline, but this didn’t seem to make near as much a dent on them as did the lack of nutrients required for them to grow in the first place. Fish densities also didn’t affect phytoplankton near as much as with the copepods.

So just as the secret to high quality cooking is knowing your ingredients and how best to combine them, these findings can help our understanding of how climate change and our actions are affecting the region. These results should be seen as only the first step in explaining these complex interactions. But by understanding them, we can make better recipes for the future. From there, we can ultimately make better choices and management plans that will help maintain a healthy, viable system in the years to come.

Master’s Degree Project in Biology 45 credits 2020
Department of Biology, Lund University

Advisor: Per Carlsson and Jessica Abbott
Advisors Aquatic Ecology and Evolutionary Ecology/Department of Biology (Less)
Please use this url to cite or link to this publication:
author
Hopkins, Stephanie
supervisor
organization
course
BION02 20191
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9006878
date added to LUP
2020-03-20 14:37:20
date last changed
2020-03-20 14:37:20
@misc{9006878,
  abstract     = {Climate change is greatly affecting the world’s seas in many ways, but of those particularly at risk, are inland seas such as the Baltic Sea. In spite of this though, there still remains a large gap in our understanding of how multiple stressors can change these systems over time. Therefore, as a way to assess how copepod and phytoplankton species groups are changing within the Kattegat, multidecadal time series analyses were conducted. Perspective top-down and bottom-up drivers were also investigated to explain their changes in density over time. The results of which, found overall declines for both phytoplankton and copepod groups, but not in cyanobacteria, p < 0.001. Decreases in the surface concentrations for both total phosphorous and total nitrogen, with an increase in temperature and salinity were also found, p < 0.001. Pairwise correlations were tested using spearman rank correlation analyses. Of which showed strong negative correlations between salinity and nutrient concentrations, and where temperature had mixed effects on nutrient concentrations, both sharing a positive relationship with phosphorous and a negative relationship with nitrogen. For all parameter combinations, general linear modelling was used. Final results suggested nutrient reductions as a potential factor in phytoplankton declines, while decreasing copepod densities were found to be best explained by predation components: sprat and herring. The inclusion of herring and sprat data also generated stronger model predictabilities with lower Akaike scores and higher adjusted r-squared values for both phytoplankton and copepod densities. This suggests their inclusion is vital for future modelling of planktonic communities.},
  author       = {Hopkins, Stephanie},
  language     = {eng},
  note         = {Student Paper},
  title        = {Understanding the past to guide the future, a community level response to climate change in the Kattegat (Baltic Sea), 1983 to 2017},
  year         = {2020},
}