No abstract

Macroalgae-based products are increasing in demand also in Europe. In the European Union, each category of macroalgae-based products is regulated separately. We discuss EU legislation, including the law on medicinal products, foods including food supplements and food additives, feed and feed additives, cosmetics, packaging materials, fertilizers and biostimulants, as well as biofuels. Product safety and consumer protection are the priorities with any new products. Macroalgae products can be sold as traditional herbal medicines. The novel food regulation applies to macroalgae foods that have not previously been used as food, and organic macroalgae are a specific regulatory category. The maximum levels of heavy metals may be a barrier for macroalgae foods, feeds, and fertilizers. Getting health claims approved for foods based on macroalgae is demanding. In addition to the rules on products, the macroalgae business is strongly impacted by the elements of the general regulatory environment such as agricultural/aquacultural subsidies, maritime spatial planning and aquaculture licensing, public procurement criteria, tax schemes, and trade agreements.

In parts of the Baltic Sea, the phytoplankton spring bloom communities, commonly dominated by diatoms, are shifting toward the co-occurrence of diatoms and dinoflagellates. Although phytoplankton are known to shape the composition and function of associated bacterioplankton communities, the potential bacterial responses to such a decrease of diatoms are unknown. Here we explored the changes in bacterial communities and heterotrophic production during the spring bloom in four consecutive spring blooms across several sub-basins of the Baltic Sea and related them to changes in environmental variables and in phytoplankton community structure. The taxonomic structure of bacterioplankton assemblages was partially explained by salinity and temperature but also linked to the phytoplankton community. Higher carbon biomass of the diatoms Achnanthes taeniata, Skeletonema marinoi, Thalassiosira levanderi, and Chaetoceros spp. was associated with more diverse bacterial communities dominated by copiotrophic bacteria (Flavobacteriia, Gammaproteobacteria, and Betaproteobacteria) and higher bacterial production. During dinoflagellate dominance, bacterial production was low and bacterial communities were dominated by Alphaproteobacteria, mainly SAR11. Our results suggest that increases in dinoflagellate abundance during the spring bloom will largely affect the structuring and functioning of the associated bacterial communities. This could decrease pelagic remineralization of organic matter and possibly affect the bacterial grazers communities.

Plankton communities and their temporal development have shifted towards earlier onset of the spring bloom and lower diatom-dinoflagellate proportions in parts of the Baltic Sea. We studied the effects of community composition and spring bloom phases on seston nutrient stoichiometry, revealing possible consequences of these shifts. Community composition, seston C:N:P:Si:chl a ratios, and physiological and environmental variables were determined for 4 research cruises, covering all major sub-basins and bloom phases. A redundancy analysis revealed that temperature and inorganic nutrients were the main drivers of community changes, and high diatom biomass was linked to low temperatures (growth phase). The effects of changing dominance patterns on seston stoichiometry were studied by applying a community ordination (non-metric multidimensional scaling and generalized additive models). C:N:P ratios increased from the growth phase (103:14:1) to the peak phase (144:18:1) and decreased after inorganic nitrogen was depleted (127:17:1). Taxonomic differences explained ~50% of changes in C:Si, N:Si, and chl a:C ratios and <30% for C:P and N:P, whereas C:N was virtually unaffected by the community composition. The fixed chl a:C range (~0.005-0.04) was largely determined by diatoms, independent of the dominant species. Thus, C:Si and N:Si could be used to estimate the share of diatoms to the seston and chl a:C to describe bloom phases and C budgets during spring. Interestingly, mixed communities featured higher C:N:P ratios than diatom-dominated ones. However, as community composition explained <30% of changes in C:N:P, we conclude that these ratios rather represent the total plankton physiology in natural plankton assemblages.

The ratio of inorganic nitrogen to phosphorus (NP) is projected to decrease in the Eastern Boundary Upwelling Systems (EBUS) due to warming of the surface waters. In an enclosure experiment, we employed two levels of inorganic NP ratios (10 and 5) for three distinct plankton communities collected along the coast of central Chile (33°S). The primary effect of the NP treatment was related to different concentrations of NO 3 , which directly influenced the biomass of phytoplankton. In addition, low inorganic NP ratio reduced the seston NP and Chl a-C ratios, and there were some effects on the plankton community composition, e.g., benefitting Synechococcus spp. in some communities. One of the communities was clearly top-down controlled and trophic transfer to grazers was up to 5.8% during the 12 day experiment. Overall, the initial, natural plankton community composition was more important for seston stoichiometry and trophic transfer than the manipulation of the inorganic NP ratio, highlighting the importance of plankton community structure for marine ecosystem functioning.

No abstract

Abstract. The Peruvian upwelling system is a highly productive ecosystem with a large oxygen minimum zone (OMZ) close to the surface. In this work, we carried out a mesocosm experiment off Callao, Peru, with the addition of water masses from the regional OMZ collected at two different sites simulating two different upwelling scenarios. Here, we focus on the pelagic remineralization of organic matter by the extracellular enzyme activity of leucine aminopeptidase (LAP) and alkaline phosphatase activity (APA). After the addition of the OMZ water, dissolved inorganic nitrogen (N) was depleted, but the standing stock of phytoplankton was relatively high, even after N depletion (mostly > 4 µg chlorophyll a L−1). During the initial phase of the experiment, APA was 0.6 nmol L−1 h−1 even though the PO43- concentration was > 0.5 µmol L−1. Initially, the dissolved organic phosphorus (DOP) decreased, coinciding with an increase in the PO43- concentration that was probably linked to the APA. The LAP activity was very high, with most of the measurements in the range of 200–800 nmol L−1 h−1. This enzyme hydrolyzes terminal amino acids from larger molecules (e.g., peptides or proteins), and these high values are probably linked to the highly productive but N-limited coastal ecosystem. Moreover, the experiment took place during a rare coastal El Niño event with higher than normal surface temperatures, which could have affected enzyme activity. Using a nonparametric multidimensional scaling analysis (NMDS) with a generalized additive model (GAM), we found that biogeochemical variables (e.g., nutrient and chlorophyll-a concentrations) and phytoplankton and bacterial communities explained up to 64 % of the variability in APA. The bacterial community best explained the variability (34 %) in LAP. The high hydrolysis rates for this enzyme suggest that pelagic N remineralization, likely driven by the bacterial community, supported the high standing stock of primary producers in the mesocosms after N depletion.

Abstract. The Peruvian upwelling system is a highly productive ecosystem that could be altered by ongoing global changes. We carried out a mesocosm experiment off Peru, with the addition of water masses from the regional oxygen minimum zone (OMZ) collected at two different sites simulating two different upwelling scenarios. Here we focus on pelagic remineralization of organic matter by extracellular enzyme production of leucine aminopeptidase (LAP) and alkaline phosphatase activity (APA). After addition of the OMZ water, dissolved inorganic nitrogen (N) was depleted, but the standing stock of phytoplankton was relatively high even after nutrient depletion (mostly >4 µg chlorophyll a L-1). During the initial phase of the experiment, APA was 0.6 nmol L-1 h-1 even though the PO43- concentration was >0.5 µmol L-1. Initially, the dissolved organic phosphorus (DOP) decreased, coinciding with an increase in PO43- concentration probably linked to the APA. The LAP activity was very high with most of the measurements in the range 200–800 nmol L-1 h-1. This enzyme degrades amino acids and these high values are probably linked to the highly productive, but N-limited coastal ecosystem. Also, the experiment took place during a rare coastal El Niño event with higher-than-normal surface temperatures, which could have affected the enzyme production. Using a non-parametric multidimensional scaling analysis (NMDS) with a generalized additive model (GAM), we found that biogeochemical variables (e.g. nutrient and chlorophyll a concentrations), phytoplankton and bacterial communities explained up to 64 % of the variability in APA. The bacterial community explained best the variability (34 %) in LAP. The high hydrolysis rates for this enzyme suggests that pelagic N remineralization supported the high standing stock of primary producers in the mesocosms after N depletion.