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Is the local fish fauna affecting the diversity and density of Fucus-associated invertebrate fauna?

Lövdén, Olof (2018) BIOM02 20172
Degree Projects in Biology
Abstract
It is generally considered that the brackish Baltic Sea has relatively low biodiversity levels of both fish and invertebrate fauna, compared to the more saline waters of Kattegat and Skagerrak on the Swedish west coast. However, a trend has been noticed, showing higher biodiversity and biomass levels of Fucus-associated fauna on the east coast of Scania, i.e. within the Baltic Sea, compared to the northwest coast of Scania, i.e. in the Kattegat area. One possible explanation to this phenomenon could be higher predation pressure from fish predators on the west coast, compared to the east. This study was conducted as an attempt to find out how the biodiversity and biomass of the Fucus-associated differs between the east and west coasts of... (More)
It is generally considered that the brackish Baltic Sea has relatively low biodiversity levels of both fish and invertebrate fauna, compared to the more saline waters of Kattegat and Skagerrak on the Swedish west coast. However, a trend has been noticed, showing higher biodiversity and biomass levels of Fucus-associated fauna on the east coast of Scania, i.e. within the Baltic Sea, compared to the northwest coast of Scania, i.e. in the Kattegat area. One possible explanation to this phenomenon could be higher predation pressure from fish predators on the west coast, compared to the east. This study was conducted as an attempt to find out how the biodiversity and biomass of the Fucus-associated differs between the east and west coasts of Scania. It also attempts to compare the amount of fish predators and their food preferences on the two coasts to see if predation pressure may explain the possible differences. The hypothesis was that more biodiversity and biomass of the Fucus-associated invertebrate fauna would be found on the east coast, and more fish predators would be found on the west coast. The east coast had significantly higher biodiversity and biomass levels of the invertebrate fauna, while more fish predators were found on the west coast, which confirmed the hypotheses. The amount of fish predators might be a part of the explanation of why there are more invertebrate fauna on the east coast. Other factors that were not considered in the project, but might have an impact on the results, are for example epiphyte algae coverage, crab predation on the west coast and wave action exposure. (Less)
Popular Abstract
Olof Lövdén

Are fish predators affecting the diversity of marine invertebrates?

The Baltic Sea has, generally been regarded as a sea with low diversity of both animals and algae, because of the brackish water and different human impacts such as added nutrients and overfishing. The salinity of the water decreases from the salty west coast to the brackish waters of the Baltic. The marine west coast is usually considered to have relatively high diversity of marine organisms. During the last few years smaller project has been performed on the marine ecology course at Lund University and they found that there was a higher diversity of invertebrate species living in proximity of brown algae on the southern Baltic coast compared to the west... (More)
Olof Lövdén

Are fish predators affecting the diversity of marine invertebrates?

The Baltic Sea has, generally been regarded as a sea with low diversity of both animals and algae, because of the brackish water and different human impacts such as added nutrients and overfishing. The salinity of the water decreases from the salty west coast to the brackish waters of the Baltic. The marine west coast is usually considered to have relatively high diversity of marine organisms. During the last few years smaller project has been performed on the marine ecology course at Lund University and they found that there was a higher diversity of invertebrate species living in proximity of brown algae on the southern Baltic coast compared to the west coast. The aim of this project was to find out if the diversity of algae-associated invertebrate species is higher on the east coast of southern Sweden, compared to the west coast. Fish predators were identified as a possible explanation of the differences in diversity. If there are more fish predators on the west coast, that might explain why the diversity of invertebrates is lower.

Bladder wrack (Fucus vesiculous) algae and fish were sampled at one site per coast. All invertebrates in the algae were collected, identified, counted and weighed. Free-swimming invertebrates were caught using traps and they were then identified, counted and weighed. Fish were also identified, counted and weighed. Afterwards the biodiversity was calculated and compared using statistical tests.

Regarding the results of the invertebrates associated with the bladder wrack, significantly higher levels of diversity and biomass was found on the east coast, compared to the west coast. On the west coast, however, a significantly higher biomass of fish predators was found. For the mobile invertebrates caught in the traps, no significant differences in diversity or biomass could be found. The results of the algae-associated invertebrates confirmed the hypothesis that higher diversity and biomass would be found on the east coast. It also opposes past theory about the diversity of organisms in Swedish seas. The hypothesis that more fish predators would be found on the west coast was also confirmed. The higher numbers of fish predators could therefor possibly explain why there are more invertebrates on the east coast.

From the literature three other factors were identified as having a possible influence on the biodiversity of invertebrates. Firstly, the abundance of filamentous algae growing on the Fucus algae can affect the invertebrates living amongst the larger algae, such as the bladder wrack. A medium amount of cover has usually lead to higher diversity of invertebrates. Secondly, green crabs (Carcinus maenas) are proven effective predators on mussels, such as the common blue mussel (Mytilus edulis). As crabs only live on the west coasts of Sweden, and not on the east coast, they could be affecting the results of the study, as mussels contributed the most to the difference in biomass between the coasts. Lastly, wave action can also affect the biodiversity of invertebrates, as too high exposure to waves can negatively affect it. None of these three factors were measured in the study but should be considered for future studies in this area. In conclusion, the main result of this study goes against the general theory that the diversity of invertebrate fauna is lower in the Baltic Sea than on the Swedish west coast and this should be studied more in the future.

Supervisor: Per Carlsson, per.carlsson@biol.lu.se
Department of Biology, Aquatic Ecology
Lund University, 30 credits (Less)
Please use this url to cite or link to this publication:
author
Lövdén, Olof
supervisor
organization
course
BIOM02 20172
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8958546
date added to LUP
2018-09-12 14:28:53
date last changed
2018-09-12 14:28:53
@misc{8958546,
  abstract     = {It is generally considered that the brackish Baltic Sea has relatively low biodiversity levels of both fish and invertebrate fauna, compared to the more saline waters of Kattegat and Skagerrak on the Swedish west coast. However, a trend has been noticed, showing higher biodiversity and biomass levels of Fucus-associated fauna on the east coast of Scania, i.e. within the Baltic Sea, compared to the northwest coast of Scania, i.e. in the Kattegat area. One possible explanation to this phenomenon could be higher predation pressure from fish predators on the west coast, compared to the east. This study was conducted as an attempt to find out how the biodiversity and biomass of the Fucus-associated differs between the east and west coasts of Scania. It also attempts to compare the amount of fish predators and their food preferences on the two coasts to see if predation pressure may explain the possible differences. The hypothesis was that more biodiversity and biomass of the Fucus-associated invertebrate fauna would be found on the east coast, and more fish predators would be found on the west coast. The east coast had significantly higher biodiversity and biomass levels of the invertebrate fauna, while more fish predators were found on the west coast, which confirmed the hypotheses. The amount of fish predators might be a part of the explanation of why there are more invertebrate fauna on the east coast. Other factors that were not considered in the project, but might have an impact on the results, are for example epiphyte algae coverage, crab predation on the west coast and wave action exposure.},
  author       = {Lövdén, Olof},
  language     = {eng},
  note         = {Student Paper},
  title        = {Is the local fish fauna affecting the diversity and density of Fucus-associated invertebrate fauna?},
  year         = {2018},
}