The methods used by researchers at NatureScot underpin our evidence base and play a crucial role in effective decision-making and management of our marine environment. Dr Kelly James tells us of a new framework used by NatureScot to investigate linkages between different Priority Marine Features. This framework was developed by Kelly during her PhD internship with NatureScot, funded by Marine Alliance for Science and Technology for Scotland.
An example of an inter-linked habitat (containing kelp, seagrass, and maerl) that is biodiverse and functionally rich. ©NatureScot
Inter-linked habitats and function diversity
Within nature, species and habitats rarely exist in isolation, with a complex array of interactions linking them. A great example of such interactions exists in inter-linked habitats, where habitats alter the physical environment to support the existence of others. Examples include linkages between bivalve and maerl beds where both habitats facilitate the presence of each other. Bivalves, such as flame shells and horse mussels, produce byssal threads which help attach their shells to surfaces. These byssal threads can stabilise sediment and bind to maerl (calcifying seaweed) which can aid the persistence of maerl beds. Inversely, maerl beds (which form complex 3D habitats) can reduce water flow, making the environment more favourable for the existence of bivalve beds. This partnership results in the formation of a complex and diverse habitat which support a range of invertebrate (i.e. crabs and starfish) and mobile species (such as commercially important juvenile fish species).
A swimming crab with a peacock worm on a maerl bed in Loch Carron. ©NatureScot
Inter-linked habitats can be more biodiverse and functionally rich compared to their isolated counterparts. By having multiple habitats within the same space, the number of species that occupy inter-linked habitats increases, increasing biodiversity. In an interlinked bivalve-maerl bed, species can occupy a variety of spaces, from living on the shells of bivalves (i.e. barnacles and seaweeds), to burrowing in the fine muddy sediment between maerl pieces (i.e. edible crabs and worms). Inter-linked habitats can also increase functional diversity - a measure of the range of things that organisms can do. The types of functions offered depend on the types of species present. For example, filter feeders (such as bivalves and sea pens) play an important role in water filtration by filtering particles from the water column. Other species, such as seaweeds, photosynthesis by taking energy from the sun and convert this to plant matter which can be fed on by a range of other species. Biodiverse habitats that are functionally rich can be more resilient to the negative pressures of climate change and thus identifying these ecologically important habitats is a crucial part of effective conservation.
An inter-linked maerl bed and seagrass bed. Both habitats play a role in stabilising the sediment and reducing water movement which aids the existence of one another. ©NatureScot
Measuring Functional Diversity
Whilst methods that measure changes in biodiversity are well established and used regularly by the scientific community, those that measure functional diversity are not. As part of my NatureScot internship I was tasked with developing a framework for measuring functional diversity, with focus on investigating the benefits offered by inter-linked habitats. To measure functional diversity I chose Biological Trait Analysis (BTA). BTA considers differences between areas by measuring the number of functions provided rather than the number of species present. This method provided a greater insight into differences between areas. For example, when only considering biodiversity, areas may seem vastly different because of changes in some dominant species. However, BTA analysis may show that whilst the species present differ, the types of functions provided do not. For example, habitats may be home to large number of brittlestars which can reshape the surface sediment and filter particles from the water column. Whilst the species of brittle stars may differ between beds the functions offered do not and therefore the sites may be functionally similar.
A horse mussel encrusted with creatures. ©NatureScot
Linkages between Priority Marine Features – a case study
During my internship, I focussed on inter-habitat linkages between flame shell and maerl beds, and between horse mussel beds and maerl beds. These habitats are known to be both ecologically and commercially important, being home to a diverse array of species including rare species, juvenile gadoids (i.e. cod and haddock) and shellfish. A range of functions can be provided by each habitat including food supply to other species, stabilising coastal sediment, storing blue carbon and filtering water. Given the importance of flame shell, maerl and horse mussel beds and their sensitivity to human disturbance (such as bottom trawling) they are currently protected in Scotland as Priority Marine Features. Whilst we have a good understanding of the diversity and functions provided by these habitats when independent from each other, little is known about how linkages between the habitats affect both biodiversity and functional diversity.
By using BTA, I was able to confirm that inter-linked habitats increase both biodiversity and functional diversity. Comparisons between independent habitats and inter-linked habitats showed that by co-existing within the same space, inter-linked habitats increased the types of species supported and the functions provided resulting in more biodiverse and functionally diverse spaces. As an incidental finding, BTA also showed that disturbance (both natural and/or anthropogenic) likely plays a role in shaping communities and their functional diversity. Exposed sites with higher wave energy and those subjected to historic bottom fishing activities were more typically inhabited by smaller species with shorter life-spans and reduced functional diversity compared to sites considered undisturbed.
A flame shell on a marl bed. ©NatureScot
The findings from the analysis provided a greater insight into the mechanisms that shape communities within the marine environment. Developing a framework for assessing functional diversity allows NatureScot to delve deeper into the diversity of our marine environment. Biodiverse habitats that are functionally rich can be more resilient to the negative pressures of climate change. Thus, measuring and identifying the drivers of biodiversity and functional diversity is crucial for effective conservation and the protection of healthy ecosystems in a warmer, more acidic world.
The full report is available on our website here: NatureScot Research Report 1213 - Exploring biological trait analysis and inter-habitat linkages in three seabed habitat PMFs in Scotland
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