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Potential of filamentous macroalgae and sessile invertebrates for bioremediation and valorization in the northern Baltic Sea

Year: 2020
Type: dissertation
Abstract: ABSTRACT High nutrient concentrations caused by human activities is a global problem in fresh and coastal waters. Large areas of the Baltic Sea are also severely eutrophicated due to the past and present nitrogen (N) and phosphorus (P) emissions; consequently, ephemeral macroalgae exist in abundance. Nutrients incorporated in the marine biomasses have potential as part of a solution for amelioration of eutrophication in a world aiming towards a circular economy. Nutrients could be circulated back to the land and used for fertilization. Collected marine biomass also has potential for several other purposes. In this thesis, I studied organisms adhering to the substratum in respect of their use for bioremediation and, furthermore, for valorization in the northern Baltic Sea’s blue economy. Article I investigates the potential of filamentous macroalgae and sessile invertebrates for bioremediation. It studied the weight of the biomass attaching to the substratum, contents of particulate organic carbon (POC), particulate organic nitrogen (PON), and particulate organic phosphorus (POP) in the invertebrate’s fraction and macroalgae as well as concentrations of arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) in the biomass. Article II focuses on the fatty acid concentrations and profiles of two green algae (Ulva intestinalis and Cladophora glomerata) and one red alga (Ceramium tenuicorne) in relation to ambient N and P availability. Article III reviews studies around the world on the potential of macroalgae in biofuel production. Biomass on the artificial substrata is almost exclusively composed of the green algae Ulva spp. and C. glomerata, the red algae Polysiphonia fibrillosa and C. tenuicorne, the brown algae Pylaiella littoralis and Ectocarpus siliculosus, the blue mussels (Mytilus trossulus), the bay barnacles (Amphibalanus improvisus), and the hydroids Cordylophora caspia and Gonothyraea loveni. Over 95% of biomass is composed of sessile invertebrates; due to this and the small size of the northern Baltic Sea macroalgae, the removal of both invertebrates and macroalgae seems the most feasible practice in the current situation. Amelioration of small-scale nutrient loads is possible. The other most feasible utilizations for the total biomass would be as fertilizer as such or after composting and as additional feed material in biogas production. The Cd content may limit the utilizable amount of biomass for the use as fertilizer as such. The Cd content varied according to the cultivation site and the incubation time. Limits set in the EU for the metals As, Cd and Pb may be exceeded if animal feed were composed exclusively of a certain fraction or fractions of biomass. Among the studied macroalgae, the lowest concentrations of all heavy metals were in Ulva spp., and it seemed to be a safe choice for solely algal-based feed applications regarding the measured metals. Fatty acid composition is important in nutrition and in the refining of high value products. This study indicates that linoleic (C18:2n-6, LA) and arachidonic (C20:4n-6, AA) acid levels in C. glomerata could be regulated by nutrient manipulation. Elevated concentrations of these fatty acids were associated with higher N availability. In practice, low biomass yield and lack of established infrastructure for cultivation, harvesting and utilization pose a challenge for a large-scale utilization of the northern Baltic Sea sessile organisms.
Language: English
Subfield: Oceanography
Open Access status: green
OpenAlex ID: W3109374874
Cites: 83
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Related to: 10