Effects of boating activities on aquatic vegetation in the Stockholm archipelago, Baltic Sea

The aquatic vegetation in 44 similar shallow and sheltered inlets exposed to different kinds of disturbances by boating was studied in a rocky archipelago in the Baltic Sea. The results indicate that both recreational boating activities and traffic by medium sized ferryboats may cause significant changes in community composition and have significant negative effects on species richness and the development of the macrophytic vegetation at greater depth. Changes in inlet morphology by dredging and increases in resuspension and turbidity by wave-action from boats were most probably the major factors contributing to the demonstrated differences in the vegetation between inlets. In inlets used as harbours for private boats (marinas) or adjacent to ferryboat routes, vegetation cover and species richness declined significantly more with depth than in reference inlets not exposed to disturbance by boating activities. In marinas, turbidity was significantly higher than in reference inlets. Accordingly, a canonical correspondence analysis showed that the abundance of species sensitive to poor light conditions, such as Chara spp. and Ruppia spp. were negatively correlated with marinas while Myriophyllum spicatum and Ceratophyllum demersum that are common in nutrient rich turbid habitats were positively correlated with marinas. Mechanical disturbance by propellers may also have contributed to the results, disfavouring Potamogeton pectinatus compared to similar caulescent species in marinas. Chara tomentosa and Najas marina that are exposure sensitive mud thriving species were negatively correlated with inlets adjacent to ferryboat routes, while the macroalga, Fucus vesiculosus that is dependent on clean substrate for successful recruitment was positively correlated with inlets adjacent to ferryboat routes. It is important to explore further the effects of boating activities in these habitat types, since the studied inlets sustain a high diversity of both plants and invertebrates and provide highly significant recruitment areas for coastal fish in the Baltic Sea. (C) 2004 Elsevier Ltd. All rights reserved

Integrating experimental and distribution data to predict future species patterns

Predictive species distribution models are mostly based on statistical dependence between environmental and distributional data and therefore may fail to account for physiological limits and biological interactions that are fundamental when modelling species distributions under future climate conditions. Here, we developed a state-of-the-art method integrating biological theory with survey and experimental data in a way that allows us to explicitly model both physical tolerance limits of species and inherent natural variability in regional conditions and thereby improve the reliability of species distribution predictions under future climate conditions. By using a macroalga-herbivore association (Fucus vesiculosus - Idotea balthica) as a case study, we illustrated how salinity reduction and temperature increase under future climate conditions may significantly reduce the occurrence and biomass of these important coastal species. Moreover, we showed that the reduction of herbivore occurrence is linked to reduction of their host macroalgae. Spatial predictive modelling and experimental biology have been traditionally seen as separate fields but stronger interlinkages between these disciplines can improve species distribution projections under climate change. Experiments enable qualitative prior knowledge to be defined and identify cause-effect relationships, and thereby better foresee alterations in ecosystem structure and functioning under future climate conditions that are not necessarily seen in projections based on non-causal statistical relationships alone.Peer reviewe

Integrating experimental and distribution data to predict future species patterns

Predictive species distribution models are mostly based on statistical dependence between environmental and distributional data and therefore may fail to account for physiological limits and biological interactions that are fundamental when modelling species distributions under future climate conditions. Here, we developed a state-of-the-art method integrating biological theory with survey and experimental data in a way that allows us to explicitly model both physical tolerance limits of species and inherent natural variability in regional conditions and thereby improve the reliability of species distribution predictions under future climate conditions. By using a macroalga-herbivore association (Fucus vesiculosus - Idotea balthica) as a case study, we illustrated how salinity reduction and temperature increase under future climate conditions may significantly reduce the occurrence and biomass of these important coastal species. Moreover, we showed that the reduction of herbivore occurrence is linked to reduction of their host macroalgae. Spatial predictive modelling and experimental biology have been traditionally seen as separate fields but stronger interlinkages between these disciplines can improve species distribution projections under climate change. Experiments enable qualitative prior knowledge to be defined and identify cause-effect relationships, and thereby better foresee alterations in ecosystem structure and functioning under future climate conditions that are not necessarily seen in projections based on non-causal statistical relationships alone

Factors structuring Fucus communities at open and complex coastlines in the Baltic Sea

This thesis deals with physical factors and biological interactions affecting the distribution of two fucoid species, Fucus vesiculosus and F. serratus, in the Baltic Sea. Studies have been carried out in two quite different environments: an archipelago, and an open rocky coast. The archipelago has an extremely long coastline with a heterogeneous submerged landscape of different substrate types, slopes, water qualities, and degrees of wave exposure. The factors influencing F. vesiculosus distribution, morphology and epiphyte composition were studied in the Stockholm archipelago using field surveys and spatial modelling in Geographic information systems (GIS). A GIS-method to estimate wave exposure was developed and validated by comparing the result to an index based on vertical zonation of lichens. Wave exposure was considered an important factor for predicting the distribution of F. vesiculosus by its ability to clean hard surfaces from silt, and a predictive model was constructed based on the information of wave exposure and slope of the shore. It is suggested that the lower distribution boundary of attached F. vesiculosus is set by sediment in sheltered parts of the archipelago, and by light availability in highly wave exposed parts. The morphology of F. vesiculosus was studied over a wave exposure gradient, and several characters responded in accordance with earlier studies. However, when separating effects of wave exposure from effects of other confounding water property parameters, only thallus width was significantly different. Several water property parameters were shown to be correlated with wave exposure in the Stockholm archipelago, and the mechanism responsible for the effects on F. vesiculosus morphology is discussed. The composition of epiphytes on F. vesiculosus varied over a wave exposure gradient with a positive correlation to Elachista fucicola, and a negative to Chorda filum. At an open coast the physical environment is much less heterogeneous compared to an archipelago. The distributions of F. vesiculosus, F. serratus, turf-forming algae, and the seafloor substrate, were surveyed along the open coasts of Öland and Gotland. Turf-forming algae dominated all hard substrates in the area, and Polysiphonia fucoides was most abundant. At the Gotland coast F. vesiculosus was less abundant than at the Öland coast, and F. serratus occurred only in the southern-most part. Fucus serratus was increasingly more common towards south which was interpreted as an effect mainly of the Baltic salinity gradient, or the variation of salinity that has occurred in the past. The effects of turf-forming algae and sediment on F. serratus recruitment at 7 m depth off the Öland east coast were studied in the field, and by laboratory experiments. Almost no recruits were found in the algal turf outside the F. serratus patches. More fine sediment was found in the turf than in the F. serratus patches, suggesting that the turf accumulates sediment by decreasing resuspension. Both filamentous algae and sediment decreased the attachment ability of F. serratus zygotes and survival of recruits, and sediment had the strongest effect. It is therefore suggested that F. serratus has difficulties recruiting outside its patches, and that these difficulties are enforced by the eutrophication of the Baltic Sea, which has favoured growth of filamentous algae and increased sedimentation. An overall conclusion is that Fucus distribution is affected by large-scale-factors, such as the eutrophication and salinity changes of the Baltic Sea, as well as by small-scale variation in wave exposure, substrate and slope, and by surface competition with neighbouring species

Inventering av vegationsklädda bottnar i gotländska kustområden 2018

Denna undersökning är en del i det regionala miljöövervakningsprogrammet. Djuputbredning av makroalger och ålgräs undersöktes med hjälp av dykinventering i syfte att följa upp miljökvalitet i fem Gotländska kustvattenområden; Fårösunds vattenområde, Östra Gotlands norra kustvatten, Östra Gotlands södra kustvatten, Västra Gotlands södra kustvatten och Västra Gotlands mellersta kustvatten.Uppföljningen har så långt som möjligt följt bedömningsgrunderna för kustvatten och vatten i övergångszon (Naturvårdsverket, 2007 a). På vissa undersökta lokaler har bedömningsgrunderna inte kunnat uppfyllas fullt ut, t.ex. till följd av grunda djupförhållanden eller att bedömningen behövt baseras på färre arter än vad bedömningsgrunderna kräver. Vilka avsteg som gjorts beskrivs i anslutning till beskrivningen av de aktuella lokalerna. För vissa lokaler har expertbedömning använts för att bedöma status. Totalt undersöktes 8 transekter, varav 2 i Fårösunds vattenområde, 3 i Östra Gotlands norra kustvatten, och en transekt vardera i Östra Gotlands södra kustvatten, Västra Gotlands södra kustvatten och Västra Gotlands mellersta kustvatten. Dessa kustvattenområden har tidigare följts upp inom den regionala miljöövervakningen 2009, 2012 och 2015 (Petersson 2010, 2013, 2016) med undantag för Östra Gotlands Södra kustvatten som inte följdes upp 2015. Beskrivningar och struktur i denna rapport följer till stor del Petersson, 2015 i syfte att underlätta jämförelser med tidigare år.I Fårösunds vattenområde och Östra Gotlands norra kustvatten klassades statusen som hög, i Östra Gotlands Södra kustvatten klassades statusen som otillfredsställande, i Västra Gotlands södra kustvatten klassades statusen som måttlig och i Västra Gotlands mellersta kustvatten klassades statusen som god.3.

Hydromorfologisk modellering av risk för båtinducerad stranderosion i Stockholms skärgård

Metoder för beräkning av hydromorfologiska kvalitetsfaktorer hos kustvattenförekomster har tidigare saknats. I denna rapport har två modeller för beräkning av vågregim och dess avvikelse från referensförhållanden utvecklats. Modellerna ger ett mått på potentiell risk för stranderosion utgående från svall- och avsänkningseffekter från kommersiell båttrafik. Modellernas tillförlitlighet verifierades via fältinventeringar av skador på stranden och vassruggar. Båda modellerna kunde framgångsrikt separera olika typer av skador. Befintlig modell av naturlig vågexponering användes för att avgränsa de områden som utpekats som potentiellt känsliga för båtinducerad stranderosion. De modellerade värdena för potentiellt erosionspåverkade stränder användes för bedömning av hydromorfologisk status. Av Stockholms läns 130 kustvattenförekomster bedömdes 38 vara av hög eller god status, 22 av måttlig, 20 av otillfredsställande och 3 av dålig status. Resultaten bör ses som en första indikation på omfattningen av potentiellt påverkad strandlinje. För en säkrare skattning krävs förbättrade, heltäckande, substratbedömningar av strandlinjen. Resultaten av projektet är utöver föreliggande rapport också GIS-filer som har levererats separat till ansvarig handläggare på myndigheten

The influence of hydrodynamic exposure on carbon storage and nutrient retention in eelgrass (Zostera marina L.) meadows on the Swedish Skagerrak coast

Cold-temperate seagrass (Zostera marina) meadows provide several important ecosystem services, including trapping and storage of sedimentary organic carbon and nutrients. However, seagrass meadows are rapidly decreasing worldwide and there is a pressing need for protective management of the meadows and the organic matter sinks they create. Their carbon and nutrient storage potential must be properly evaluated, both at present situation and under future climate change impacts. In this study, we assessed the effect of wave exposure on sedimentary carbon and nitrogen accumulation using existing data from 53 Z. marina meadows at the Swedish west coast. We found that meadows with higher hydrodynamic exposure had larger absolute organic carbon and nitrogen stocks (at 0–25 cm depth). This can be explained by a hydrodynamically induced sediment compaction in more exposed sites, resulting in increased sediment density and higher accumulation (per unit volume) of sedimentary organic carbon and nitrogen. With higher sediment density, the erosion threshold is assumed to increase, and as climate change-induced storms are predicted to be more common, we suggest that wave exposed meadows can be more resilient toward storms and might therefore be even more important as carbon- and nutrient sinks in the future.publishedVersio