En av de största utmaningarna för Östersjöregionen gäller bekämpningen av övergödning orsakad av människors utsläpp av näringsämnen till havet. Övergödningen har flera allvarliga konsekvenser för miljön, inte minst enorma algblomningar samt stora mängder alger och tång som så småningom spolas upp längs Östersjöns stränder och börjar förmultna. På gotländska kallas dessa organiska massor på stränderna för “släke” och ses oftast som ett problem då de kan försämra kustmiljön och störa turister och lokalbor som vill bada eller vistas på stranden. Släken är dock rik på näring, och att skörda släken för att använda den som en resurs skulle kunna bidra till att skapa cirkulära flöden då näring återtas från havet, samtidigt som stranden rensas och släken kan bli en potentiellt värdefull resurs som exempelvis jordförbättringsmedel eller biobränsle. Det finns dock flera hinder i vägen för att få till en hållbar skörd och användning av släke.  Projektets syfte är att undersöka vilka möjligheter som finns för att på ett hållbart sätt skörda och använda släke som en bioresurs på Gotland. Detta gjordes dels genom att identifiera hinder och incitament för släkeskörd med hjälp av en litteraturstudie över släkeskörd i Östersjöområdet samt genom en intervju med en person som arbetar med släkehanteringsfrågan i Gotlands länsstyrelse. Det undersöktes även genom en fallstudie där hinder identifierades och utvärderades för att uppskatta möjligheterna för släkeskörd inom ett valt studieområde på Gotlands östkust.  Ett flertal hinder för skörd och användning av släke kunde identifieras i litteraturstudien, som sedan delades in i de följande huvudsakliga kategorierna: skräp, erosion, biologisk mångfald, maskiner, kostnader, juridiska hinder, tidspress, kvalitet, logistik samt tungmetaller. Resultat från intervjun styrker att flera av dessa hinder är aktuella på Gotland, däribland biologisk mångfald som kan riskera att ta skada vid skörd och avlägsnande av släke, olika juridiska hinder för att få bidrag för att skörda släke, och det potentiella innehållet av tungmetaller i släke som kan begränsa dess användning, bland annat. I fallstudien framkom det att några av de viktigaste hindrena är juridiska hinder i form av olika naturskydd, som exempelvis naturreservat, som begränsar eller på andra sätt påverkar möjligheten att skörda släke. Risk för erosion genom bortförande av sand samt kostnader i samband med skörd med maskiner är ytterligare faktorer som påverkar lämpligheten för släkeskörd. Även inblandning av antropogent skräp i släken togs upp.  En slutsats som kan dras är att det finns många fördelar men även många hinder kring skörd och användning av släke. För att kunna avgöra huruvida det är möjligt att skörda och använda släke på ett hållbart sätt behöver skördeområdet först analyseras utifrån dessa hinder och sedan vägas mot fördelarna. Fallstudien visade att stränderna i studieområdet hade olika förutsättningar för hållbar släkeskörd utifrån de studerade hindrena. Flera hinder kunde dock inte appliceras på studieområdet på grund av bristande data, och det går därför inte att dra någon fullvärdig slutsats om hållbar släkeskörd i studieområdet. / One of the biggest challenges for the Baltic Sea region concerns the mitigation of eutrophication induced by nutrient emissions caused by humans. Eutrophication has numerous severe impacts on the environment, such as massive macroalgal blooms that contribute to the presence of large amounts of algae and seaweed that are eventually washed ashore on the Baltic Sea coast where they begin decomposing. On Gotland, these organic masses are called “släke”, beach wrack or beach cast in English, and are usually considered a nuisance as they can bother beach tourists. Beach cast is however very rich in nutrients, and harvesting beach cast to use it as a resource could contribute to creating circular flows as nutrients are removed from the sea while simultaneously the beach is cleaned and the beach cast could pose a potentially valuable resource useful for soil improvement or biofuel, for example. There are, however, several obstacles in the way of sustainably harvesting and using beach cast. The purpose of this project is to investigate the available possibilities to sustainably harvest and use beach cast as a bioresource on Gotland. This was done partly by identifying obstacles and incentives for beach cast harvesting in the Baltic region using a literature study as well as an interview with a government figure on Gotland. It was also explored through a case study where these obstacles were used to estimate the possibility of harvesting beach cast in a chosen study area on the east coast of Gotland. Several obstacles for harvest and use of beach cast could be identified in the literature study and were then divided into the following main categories: trash, erosion, biodiversity, machines, costs, juridical obstacles, time constraint, quality, logistics and heavy metals. Results from the interview corroborate that many of these obstacles are present on Gotland, among others, biodiversity that is susceptible to damage caused by harvesting or the removal of beach cast, various juridical obstacles to attain funding, and the potential contents of heavy metals in beach cast that can limit its possible uses. The case study also showed that some of the most important obstacles are juridical obstacles such as different forms of environmental protection such as nature reserves, that limit the possibility to harvest beach cast. The risk of erosion through removal of sand and costs due to harvesting with machines are other factors that affect the suitability of harvesting beach cast. Also, anthropogenic trash mixed in with the beach cast was mentioned. A conclusion that can be drawn is that there are many advantages as well as obstacles when it comes to harvest and use of beach cast. To be able to harvest and use beach cast in a sustainable manner the harvest site needs to be analyzed using these obstacles and be weighed against the advantages in order to determine whether harvesting is suitable. The case study also showed that different beaches have different qualifications for sustainable beach cast harvesting based on the obstacles. Several of the obstacles found in literature or from the interview couldn’t be applied to the study area, however, due to limited data, and therefore it is not possible to draw any exclusive conclusions concerning sustainable beach cast harvesting in the area.

This thesis examines the interactions of two non-indigenous algae, Mazzaella japonica and Sargassum muticum, where they co-exist and their impacts on native species in their recipient habitats. Field and lab experiments were conducted to determine if they impact native seaweed communities, marine invertebrates, and supralittoral regions. In situ studies conducted in areas where Mazzaella japonica exists without Sargassum muticum found that removal of M. japonica allowed for an increase of native seaweed abundance and richness growing in fully subtidal regions, but had no detectable impact on native seaweeds growing in intertidal regions. Additionally, at the intertidal site, removal of M. japonica resulted in the recruitment of S. muticum. In regions where the two non-indigenous seaweeds co-exist, removal of both non-indigenous seaweeds negatively impacted native seaweeds. The magnitude of this negative impact was greater in subtidal compared to intertidal regions. M. japonica removal had a greater impact on native seaweed recovery than did S. muticum removal in areas of co-existence. Removal of Mazzaella japonica also allowed for a significant increase in percent cover of Sargassum muticum at both sites where these two seaweeds co-exist. An increase in percent cover of M. japonica was found at the subtidal site when S. muticum was removed. Though both species increased when reprieved from competition with the other non-indigenous species, removal of M. japonica had a far greater influence on the increase in cover of S. muticum. This suggests that M. japonica is the dominant competitor in the ecosystem outcompeting S. muticum. Field surveys found Mazzaella japonica was the dominant wrack species washing up on beaches in Baynes Sound. Though Sargassum muticum is also a component of the wrack, it has a disproportionately large influence as a spatial subsidy on beach habitats. S. muticum decayed and decomposed at a faster rate than M. japonica and all native seaweeds tested except for Chondracanthus exasperatus. Additionally, S. muticum was colonized by significantly more invertebrates than either M. japonica or Fucus spp. Results from these studies are intended to provide information for resource managers making policy decisions regarding the fate of these two non-indigenous species. / Graduate / 0329

Accumulations of seagrass, macroalgae and other matter, collectively known as wrack, commonly occur on many sandy beaches, and can play an important role in coastal and nearshore ecosystems. Despite this, wrack removal from sandy beaches is a widespread and increasingly common practice globally, and there is little information regarding the ecological effects of such wrack removal on sandy beaches. The aim of this thesis was to establish the ecological importance of wrack in South Australian (SA) sandy-beach ecosystems. As a first step in furthering our understanding of the effects of wrack removal, I aimed to assess the importance of wrack, independent of the effects of wrack removal. The second over-riding aim of this thesis was to assess the ecological effects of wrack removal on aspects of these systems. To date, the methods used for quantifying the size of wrack deposits on sandy beaches have had limited use due to the time and expertise required to conduct thorough sampling. In Chapter 2, I thus tested the accuracy of a rapid “photopoint” method to visually estimate percentage wrack cover as well as provide an archived record. Comparisons of results obtained from conventional transects with those from photopoints indicated that the photopoint technique can be used to rapidly and accurately estimate % wrack cover on sandy beaches. The photopoint method has a wide range of potential applications and represents a valuable advance in the field. Currently our knowledge of the amounts and types of wrack on SA shores is limited, despite these accumulations being a feature of some SA beaches. Wrack deposits in three biogeographical regions of SA were thus repeatedly surveyed to assess spatial (between and within regions) and temporal (seasonal and inter-annual) variation (Chapter 2). Both wrack cover and the composition of wrack deposits varied spatially and temporally. Wrack deposits contained a diverse array of seagrass, algal, other biotic materials and anthropogenic debris. The South East region of SA had distinctly-different wrack deposits compared to the Metropolitan and Fleurieu Peninsula regions; in general, the cover of wrack was higher, and the diversity and biomass of kelps, red algae and green algae was higher in this region compared to the other two regions. South Australian wrack deposits are thus dynamic and complex. The amount of wrack deposited and retained on a beach may be affected by the beach morphology but, to date, few studies have investigated this link. I assessed wrack cover on beaches with a range of morphodynamic types and found that beaches that were more dissipative in nature had a greater cover of wrack than beaches of the reflective type. I also examined whether wrack deposits affected the sediment characteristics of underlying and nearby sediments. Wrack deposits had little measurable effect on underlying sediments and did not affect particle-size distribution or organic-matter content. There was, however, a trend for beaches in the South East region of SA to have higher organic matter content in their sediments, and these beaches also have higher wrack cover and higher proportions of algae in their deposits. There was also a trend for beaches with higher wrack cover to have less compacted sediments, although this trend was not consistent. Overnight pit-fall trapping surveys of the macrofauna on four SA sandy beaches indicated that local macrofaunal communities were diverse (representing 72 species from 19 Orders in total), abundant, and variable in both time and space. The macrofauna encountered were mostly terrestrial taxa with only 2 truly marine species, and spanned multiple trophic levels, concurring with the results of previous studies. Macrofaunal abundances were higher where associated with wrack than in bare sand, and macrofaunal communities differed between the driftline of wrack and wrack patches away from the driftline. Within the driftline itself, there were few differences between bare sand and wrack-covered areas, suggesting that the entire driftline area is important as a habitat and food resource. Thus, wrack deposits provide an important habitat and food source for macrofauna, and the driftline provides an area of beach with concentrated resources, which in turn concentrates a distinct macrofaunal community. Wrack deposition on sandy beaches varies spatially and is affected by morphological features on the beach-face such as cusps. In Chapter 5, I thus tested a series of hypotheses regarding the differences in wrack deposits, sediments and macrofaunal communities between cusp bays and horns. Bays had greater cover and larger pieces of wrack than horns. Sediment organic-matter content was greater on horns than in bays but mean particle size did not differ consistently between bays and horns. Macrofaunal diversity was higher in bays and this pattern was probably driven by differences in the cover of wrack between bays and horns. Cusp morphology thus influences the distribution of wrack on the beach-face, which in turn influences the distribution of macrofauna. Studies of sandy beaches with cusps should therefore be explicitly designed to sample cusp features and their associated wrack deposits. Chapter 6 assesses the incorporation of wrack into beach and nearshore ecosystems via two pathways: decomposition and incorporation into trophic webs. I assessed the decomposition of algal and seagrass wrack using litterbag experiments and found that after a very rapid initial loss of mass, likely due to cell lysis and leaching, the rate of decomposition of wrack was much slower. Most release of nutrients from organic matter decay thus appears to occur in the first few days after deposition and the processes affecting the rate and nature of wrack decomposition vary among taxa (i.e. algal versus seagrass and among species). Stable isotopes of C and N were used to assess whether beach macrofauna or nearshore macro-invertebrates and fish might rely on wrack as a source of nutrition. I found that seagrasses did not provide a food source for any consumers but algae, particularly brown algae including kelps, appeared to be potential sources of nutrition for beach and nearshore consumers. The incorporation of wrack into beach and nearshore ecosystems may thus occur primarily through consumption of algal wrack by herbivores such as amphipods and dipterans, with predation on them being important pathways for the transfer of nutrients and energy into higher trophic levels. The amount of wrack in the surf zone did not affect the abundance and species richness of fish and invertebrates netted there. The aim of Chapter 7 was to determine the effects of wrack removal on sandy beach macrofaunal communities. In the first study the effects of large-scale commercial harvest of wrack on the macrofaunal communities at Kingston were assessed. The macrofaunal communities present in the ‘Natural’ area of Kingston beach were far more diverse and abundant, and included different species, compared to the ‘Cleared’ area at Kingston. In the second part of Chapter 7, I experimentally removed wrack from the driftline of beaches to assess short-term effects on macrofaunal communities. The experimental treatment did not appear to have any measurable effects on the macrofaunal communities. I also analysed material that was removed from the beach in the raking experiments and found that a large proportion of the material (e.g. 81% of the DW) was sand. I recommend that future studies into the effects of wrack removal use large cleared areas of beach, attempt to use the same wrack removal methods and/or machinery used locally, and assess the macrofaunal communities repeatedly and over longer times following wrack removal activities. In Chapter 8, I attempt to assess the effects of removal of wrack for beach ‘cleaning’ or commercial ‘harvest’ of wrack by comparing key indicators from Chapters 2 to 7. Implications and recommendations for the management of wrack are discussed, including with regard to the techniques used in this thesis and their applicability in managing wrack deposits. I attempt to identify the shortcomings of this research as well as directions for further research. Thus I have demonstrated that wrack in SA provides an important link between offshore habitat and nearshore, beach and terrestrial habitats via the transfer of organic matter and nutrients. Wrack interacts with beach morphology and sediments, provides habitat for macrofauna, remineralises nutrients through its decomposition, and provides the basis of a complex trophic web. I conclude that wrack is a key component in beach ecosystems.

Diss. Univ. Innsbruck, 2006. / Zugl. Diss. Univ. Innsbruck, 2006. Literaturverz.

This thesis examines the contribution of a non-indigenous red alga, Mazzaella japonica, to wrack subsidies in Baynes Sound, British Columbia, and the effects of its removal by a commercial beach-cast harvest. Field and laboratory work was conducted to determine: 1) How large wrack inputs are in terms of biomass and spatial extent within the harvest region, and what proportion of this is comprised of M. japonica; 2) how wrack characteristics influence associated macrofauna communities; 3) if there is any detectable effect of beach-cast harvesting on either the wrack characteristics or macrofauna communities; and 4) if M. japonica provides a food source for native invertebrate consumers within the subtidal and supralittoral zones. Field surveys conducted from November 2014 through March 2015 found that wrack biomass within the harvest region could reach as much as 853 kg (±173 SD) per meter of shoreline, and cover up to 35 m2 (± 3 SD) of beach surface within this area. The macrophyte composition of the wrack was dominated by M. japonica, which accounted for 90% of the identifiable macrophyte biomass on average. Wrack in the later stages of decomposition hosted the most speciose and diverse assemblages of macrofauna, though community composition also differed among collection sites and with depth of the wrack. Though we were limited in our ability to disentangle the effects of beach-cast harvesting due to a concentration of effort at one site, we failed to detect any large influence on wrack biomass or macrofauna communities. Harvesting does, however, appear to be associated with a greater area of wrack cover and decreased mean depth. Stable isotope mixing models estimated that M. japonica contributed no more than 22% and 17% on average to the diets of supralittoral and subtidal consumers respectively, despite its overwhelming dominance in both environments. These results suggest that the non-indigenous red alga may experience a reprieve from herbivory within the subtidal environment. A lack of consumption within the supralittoral zone could influence nutrient cycling on recipient beaches and increase propagule pressure in the surrounding regions. Results from these studies are intended to help inform the management of M. japonica and its commercial harvesting. Combined, they indicate that this non-indigenous seaweed does not provide a substantial subsidy in the form of food provision for resident invertebrates. Furthermore, the commercial removal of M. japonica is small compared to the total biomass available, and had no detectable effect on the wrack-associated macrofauna communities examined. / Graduate / 2017-08-19 / jjulin.holden@gmail.com

The equilibrium theory of island biogeography provides a useful model for understanding patterns of species richness on island systems and analogous fragmented terrestrial habitats. However, like all models, it is limited in its ability to explain island species richness patterns when nutrients move across ecosystem boundaries. Recently, enhancements to the theory have been proposed, including the subsidized island biogeography hypothesis. This hypothesis suggests that nutrient subsidies from the marine environment may impact the productivity and diversity of small islands. Sea wrack (dead, shore-cast seaweed) is a recognized vector of marine-nutrient subsidies to islands in regions of low in situ productivity, but little is known about the mechanisms surrounding sea wrack accumulation in productive, temperate environments. In this research I explore the spatial and temporal distribution of sea wrack on islands along British Columbia’s temperate Central Coast. Through an observational study I investigate three broad factors that could affect sea wrack deposition: climatic patterns, physical characteristics of shorelines, and the amount of nearby donor habitat. I surveyed sea wrack biomass and species composition, as well as the biogeographical characteristics of shorelines across 455 sites on 101 islands. I returned to a subset of sites on a bi-monthly basis to document temporal changes in wrack biomass and species composition. My results demonstrate that sea wrack accumulations were present at sites that were not composed of rock substrate, and that had wide, wave protected shorelines and high amounts of nearby donor ecosystem habitat. Additionally, sea wrack biomass and species composition was ubiquitous throughout all seasons. These results suggest that sea wrack can be considered a press subsidy as it is a consistent vector of nutrients to beaches along the Central Coast. Ecological research on macrophytes, macroalgae and sea wrack often requires the conversion of wet biomass to dry, to create consistency across investigations. This is a laborious process. Here, I present the results of wet-dry calibrations for 12 common macrophyte and macroalgae species collected from the Northeast Pacific Ocean. Future investigators can use the correction factors derived from these results for estimating dry biomass, reducing the need to conduct wet-dry calibrations for each new macrophyte, macroalgae, or sea wrack study. / Graduate

Coastlines are particularly susceptible to the necessary trade-offs which occur between different ecosystem services. Should the areas be managed for biodiversity or for people? Where sandy beaches are found there is usually a management decision to be made between managing for recreation or for biodiversity. Many popular tourist beaches (particularly those with a Beach Award) are often groomed with mechanical equipment to remove any stranded seaweed and associated litter which can get entangled in the wrack. This is likely to be having a negative impact on coastal biodiversity, with wide ranging implications for the entire habitat, including the intertidal zone, sand dunes and shorebirds. Beached wrack should be allowed to naturally decompose providing a habitat for numerous species of macro-invertebrates. These macro-invertebrate communities not only include many endemic species found exclusively along the strandline but they also provide a very rich source of food for shorebirds. The re-mineralised nutrients resulting from the decomposed macrophytes should then become available to provide a rich source of nutrients to dune, strandline and marine ecosystems populations of the strandline. In previous studies grooming has been shown to have a negative impact on the invertebrates of the strandline and this study reveals that tidal range has an effect on the impacts of grooming with a higher tidal range having a more negative impact on the invertebrates. A study to observe the impacts of grooming on both adult plant and seed bank communities of the sand dunes found that grooming is having a negative impact on these populations. Grooming is predominantly driven by beach managers who aspire to gain Beach Awards in order to attract tourists to their beaches. Using non-market valuation in the form of a stated preference choice experiment and a travel cost model, it was observed that Beach Awards are not valued by beach goers but are instead influenced to visit a particular beach by good bathing water quality, high levels of biodiversity and low levels of litter. It was also shown that stranded seaweed on the beach does not deter visitors. Future management suggestions include attempting to reduce the confusion arising from the presence of multiple beach awards by either removing them altogether or by making their criteria more clear and direct with consistency in their design and designation. Bathing water quality should be completely removed from the Beach Award system and real-time information in the form of electronic signage and a publicly available App should replace it.

Världsbefolkningens tillväxt sätter stort tryck på livsmedelsproduktionen. För att bemöta den ökande efterfrågan på mat förbrukas stora mängder handelsgödsel i syftet att stimulera tillväxten hos grödor och öka jordbruksmarkens bördighet. Överkonsumtion av gödsel inom jordbruket har bidragit till växtnäringsläckage och eutrofieringen av Östersjön. En konsekvens av övergödning är ökad tillväxt av sjögräs och tång. Särskilt stora mängder av ilandflutet sjögräs och tång (även kallat släke) ansamlas på Gotlands stränder. Dessa makroalger är rika på mineraler och näringsämnen, som dessutom är viktiga för växternas ämnesomsättning och tillväxt. Genom att samla in och använda släke som gödsel kan näringen som algerna tagit upp återföras till marken och därmed återvinnas. För att öka intresset för släke som biogödsel är det därför viktigt att alternativet är ekonomiskt lönsamt och konkurrenskraftigt på gödselmarknaden.  Denna studie syftar till att undersöka vilka förutsättningar biogödningsmedel från släke har att bli ett ekonomiskt hållbart alternativ till handelsgödsel. Med en litteraturstudie som utgångspunkt är målet att skapa en modell för att jämföra priset på släkegödsel och handelsgödsel. Resultatet visade att handelsgödsel, för tillfället, betraktas som en mer attraktiv marknadsvara än släkegödsel. Trots vissa begränsningar bedöms släkegödsel ha potential att konkurrera med handelsgödsel och förhoppningsvis stärka sin position på gödselmarknaden i framtiden. Exempelvis genom att blanda in släke med konstgödsel för att minska näringstillförseln till havet och återvinna näringen som redan finns i jordbrukskretsloppet. / Rapid world population growth has caused excessive pressure on the food industry. To meet the increasing demand for food a substantial amount of commercial fertilizer is used to stimulate the growth of crops and boost the fertility of agricultural lands. Overconsumption of fertilizers has contributed to nutrient leakage and eutrophication of the Baltic Sea. Consequently, the phenomenon has led to increased growth of seaweed and seagrass, particularly in the coastal areas of Gotland where it accumulates after being washed up from the sea (also called beach-wrack). These macroalgae are rich in minerals and nutrients, which are important for the plants' metabolism and growth. By collecting and using beach-wrack as a biofertilizer, the nutrient uptake by algae can therefore be returned to the soil and thus recycled. To enable the use of biofertilizers from beach-wrack within agricultural practices, it needs to be economically profitable and competitive on the market of commercial fertilizers.  This study aims to investigate the preconditions for biofertilizers from beach-wrack to become an economically sustainable alternative to commercial fertilizers. With a literature study as a basis, the goal is to create a model for comparing the price of beach-wrack fertilizer and commercial fertilizers. The result showed that commercial fertilizers are considered to be more attractive on the fertilizer market than beach-wrack fertilizer. Despite the limitations of algae-biofertilizer, beach-wrack could have the potential to compete with commercial fertilizer alternatives in the future and hopefully strengthen its position on the fertilizer market. For instance, by mixing the beach-wrack with mineral fertilizers, thus reducing the supply of nutrients to the sea, and recycling the nutrients that are already present in the agricultural cycle.