Vivian Husa

The newly introduced species Heterosiphonia japonica Yendo (Dasyaceae, Rhodophyta): geographical distribution and abundance at the Norwegian southwest coast

The newly introduced red alga Heterosiphonia japonica, previously denoted as Dasysiphonia sp., has, since its first record in Europe in 1994, established populations in the Netherlands, Spain, France and Norway. In order to investigate the geographical distribution of the species along the Norwegian southwest coast, 83 localities were dredged along a total distance of 830 km, and the abundance of H. japonica recorded on a semi‐quantitative scale in 2000–2001. H. japonica was present in the entire range investigated. The local abundance of H. japonica at 40 localities in an area south of Bergen was recorded by dredging. H. japonica was not present at wave‐exposed localities, but was abundant at the more sheltered localities where it could constitute up to 65% of the total algal content of the dredge. The size distribution in a population was also studied at one locality during 1 year. Plants in good condition were found throughout the year and a large number of plantlets were present during all seasons. The results of this study suggest that the species has a high dispersal and recruitment capacity. The effect of H. japonica on indigenous ecosystems has yet to be determined.

Changes of macroalgal biodiversity in sublittoral sites in southwest Norway: impact of an introduced species or higher temperature?

Abstract The Pacific red alga Heterosiphonia japonica has dispersed rapidly along European shores. Due to the species’ high abundance in many habitats, an impact on species richness and composition of local macroalgal communities might be expected. Higher sea temperatures may also influence local macroalgal composition, by providing more favourable conditions for species requiring higher temperatures. Macroalgal composition at 22 sublittoral sites along the south-western coast of Norway investigated prior to the establishment of H. japonica (1994–1995) were reinvestigated in 2003–2004, using similar methods. The total number of species collected in the area was approximately the same in the present investigation as in the previous study. With regard to number and composition of species at each site, there were no significant differences between sites with high abundance of H. japonica and sites with low or no abundance. Similarity percentage analysis (SIMPER) showed that there were temporal changes in composition of the macroalgal communities, mainly caused by higher frequency of ‘southern species’ (species with a northern limit on our coast). There was a significant increase in the percentage share of such species in the reinvestigations. The temporal differences observed are most likely caused by several warm summers/autumns and mild winters since the first investigation, which may favour a higher abundance of ‘southern species’. Heterosiphonia japonica was the most important species contributing to temporal dissimilarity in the area. This paper concludes that H. japonica has caused no negative impact on regional algal species richness in the relatively short time span since its introduction.

Regional impact from fin-fish farming in an intensive production area (Hardangerfjord, Norway)

Abstract The Hardangerfjord is one of the largest salmon-farming areas in Norway, with an annual production of approximately 70,000 metric tonnes. The regional impact of fin-fish farming in a fjord environment was studied during 2008–2010. Ecological conditions in intertidal macroalgal and benthic deep basin communities were studied in addition to measurements of nutrients and chlorophyll-a values. Macroalgal communities in the intertidal zone and the deep water fauna communities showed a high ecological status in the intermediate part of the fjord and a good status in the inner part of the fjord. Faunal communities in the outermost basin indicate that the assimilative capacity for farm waste of this deep basin could be limited. Nutrients and chlorophyll-a values were within national thresholds defined as high water quality. The good ecological conditions of the parameters studied in the fjord show little evidence of a regional impact from the fish farming industry despite the intensive production level.

Historical changes in macroalgal communities in Hardangerfjord (Norway)

Abstract Hardangerfjord is the second largest fjord in Norway and is situated on the southwest coast. During the last century the fjord has been influenced by a variety of anthropogenous activities such as industry, hydro-electrical power plants and since 1980 an increase in fish farming. This study was carried out in order to investigate whether changes in the macroalgal communities of Hardangerfjord have taken place since the 1950s. The macroalgal composition at a number of stations investigated in 2008–2009 was compared to recordings from the same stations during the 1950s. While the distribution and abundance of dominant groups (fucoids, kelps) showed a high resilience when compared to recordings from the 1950s, some changes in the macroalgal communities in the fjord were evident. The present study showed higher species richness and a higher frequency of species with a warm-water affinity. Since the first part of the 1990s an increase in summer sea surface temperatures has taken place in the area, and the observed algal changes suggest a pronounced temperature effect on macroalgal communities. A number of red algal species was observed to protrude further into the fjord in the present study than in the 1950s, probably caused by altered salinity regime due to the electrical power industry.

Interactions between Salmon Farming and the Ecosystem: Lessons from the Hardangerfjord, Western Norway

Fjords are unique coastal landscape structures that require enhanced basic and applied biological research (Brattegard et al. 2011). In Norway, efforts have recently been made to study selected fjord systems more effectively and integratively. The current Thematic Issue presents results focusing on the Hardangerfjord in western Norway. The Hardangerfjord is approximately 180 km long and 2–10 km wide and is the second largest fjord in Norway. It was formed by glacial activity, has two moraine sills of around 150 m depth in the outer parts and extends to a maximum depth of 830 m in the fjord basin. In the inner part the main fjord splits into several narrow side fjords, the longest being Sørfjord which is 40 km long. Several large rivers run into the fjord and in the side fjords the surface water is permanently brackish. The rich populations of fish and shellfish have provided food and work since the times of the first recorded settlement, about 8000 years ago. The Hardangerfjord region provides good opportunities for industrial activities based on both the tributary freshwater systems and the main fjord. Consequently, the fjord basin may be affected by a number of local anthropogenic activities, such as agriculture, aquaculture, fisheries, hydroelectric power production, pollution from households and industry, and also through more indirect mechanisms such as climate change. Following the beginning of hydroelectric power plant constructions, the production of carbide and later dicyanamide was begun in the innermost part of the Sørfjord in 1908; later, other industrial plants began production in the fjord. The industrial activity resulted in strong pollution by heavy metals in the inner parts of the Hardangerfjord (Ruus et al. 2012). The discharges of black lime waste resulted in extremely low oxygen concentrations, high nitrate levels and toxic flagellate blooms in the late 1990s (Aure & Pettersen 1998). Piles of black lime waste still remain in the fjord, but the ecosystems are in recovery (Ruus et al. 2006). The massive hydroelectric power production in many rivers has provided much public revenue for local communities. The production clearly affects the habitats and life of Atlantic salmon and brown trout, while less is known about its effect on the fjord ecosystem. The Hardangerfjord is at present one of the regions in Norway with the highest density of salmon farms, with a production that exceeded 80,000 tonnes in 2011 (Knut Johnsen, The Norwegian Directorate of Fisheries, pers. comm.) or about 10,000 times the production of wild Atlantic salmon in the fjord. With high human activity in the coastal zone, the fast expansion of salmon farming along the Norwegian coast and particularly in the Hardangerfjord, the reports of massive salmon lice infection on anadromous brown trout (Salmo trutta), disease problems in many salmon farms and numerous of escapees in salmon rivers, there has been a strong concern among the public and management authorities for the wild salmon, the anadromous brown trout and the environment of the Hardangerfjord. Coincidentally, there are reports of excessive growth of filamentous macroalgae in the middle part of the fjord. The interdisciplinary research programme ‘Ecological Processes and Impacts Governing the Resilience and Alternations in the Porsangerfjord and the Hardangerfjord – EPIGRAPH’ was therefore initiated by the Ministry of Fisheries and Coastal Affairs in 2008 to learn more about the interactions between human activity and the ecosystems of the fjords. To distinguish between changes caused by local salmon farming and more general, large-scale trends related to climatic changes, the project was designed as an interdisciplinary project with eight work packages: (1) Physical oceanography and its importance for fjord ecology; (2) Nutrients, fluorescence and benthos; (3) Temporal changes in macroalgal vegetation in the intertidal and shallow subtidal zone; (4) Valuable and sensitive habitats; (5) Zooplankton and sprat diet; (6) Fish resources and predation; (7) Population structure and genetic relationship between fjord and open water components of sprat; and (8) Interactions between salmon farming and wild anadromous salmonids. The project was then linked up to other supplementary projects conducted at the Institute of Marine Research, Bergen, such as monitoring of salmon lice on wild and farmed salmonids, oceanography, Marine Biology Research, 2014 Vol. 10, No. 3, 199–202, http://dx.doi.org/10.1080/17451000.2013.840730