Microbial processes in a high-latitude fjord (Kongsfjorden, Svalbard) : II. Ciliates and dinoflagellates

This paper is part of Lena Seuthe's doctoral thesis, which is available in Munin at http://hdl.handle.net/10037/3777The composition and ecological role of ciliates and dinoflagellates were investigated at one station in Kongsfjorden, Svalbard, during six consecutive field campaigns between March and December 2006. Total ciliate and dinoflagellate abundance mirrored the seasonal progression of phytoplankton, peaking with 5.8 9 104 cells l-1 in April at an average chlorophyll a concentration of 10 lg l-1. Dinoflagellates were more abundant than ciliates, dominated by small athecates. Among ciliates, aloricate oligotrichs dominated the assemblage. A large fraction ([60%) of ciliates and dinoflagellates contained chloroplasts in spring and summer. The biomass of the purely heterotrophic fraction of the ciliate and dinoflagellate community (protozooplankton) was with 14 lg C l-1 highest in conjunction with the phytoplankton spring bloom in April. Growth experiments revealed similar specific growth rates for heterotrophic ciliates and dinoflagellates (\0–0.8 d-1). Food availability may have controlled the protozooplankton assemblage in winter, while copepods may have exerted a strong control during the post-bloom period. Calculations of the potential grazing rates of the protozooplankton indicated its ability to control or heavily impact the phytoplankton stocks at most times. The results show that ciliates and dinoflagellates were an important component of the pelagic food web in Kongsfjorden and need to be taken into account when discussing the fate of phytoplankton and biogeochemical cycling in Arctic marine ecosystems

[Corrigendum to] Effects of small-scale turbulence on lower trophic levels under different nutrient conditions [vol 32, pg 197, 2010]

Small-scale turbulence affects the pelagic food web and energy flow in marine systems and the impact is related to nutrient conditions and the assemblage of organisms present. We generated five levels of turbulence (2*10 29 to 1*10 24 W kg 21 ) in land-based mesocosms (volume 2.6 m 3 ) with and without additional nutrients (31:16:1 Si:N:P m M) to asses the effect of small-scale turbulence on the lower part of the pelagic food web under different nutrient conditions. The ecological influence of nutrients and small-scale turbulence on lower trophic levels was quantified using multivariate statistics (RDA), where nutrients accounted for 31.8% of the observed biological variation, while 7.2% of the variation was explained by small-scale turbulence and its interaction with nutrients. Chlorophyll a, primary production rates, bacterial production rates and diatom and dinoflagellate abundance were positively correlated to turbulence, regardless of nutrient conditions. Abundance of autotrophic flagellates, total phytoplankton and bacteria were positively correlated to turbulence only when nutrients were added. Impact of small-scale turbulence was related to nutrient con- ditions, with implications for oligotrophic and eutrophic situations. The effect on community level was also different compared to single species level. Microbial processes drive biogeochemical cycles, and nutrient-controlled effects of small-scale turbulence on such processes are relevant to foresee altered carbon flow in marine systems

Kartlegging av fremmede marine arter i Rogaland

The method Rapid Coastal Survey was applied in 36 marinas in the county of Rogaland during five days in august 2010. 27 introduced species were targeted in this investigation. No new species to Norway was found, but six species already established in Norway were observed at a number of sites. The ascidian Styela clava, native to northwest Pacific, was recorded at eleven sites in the county, and was most abundant at sites near Stavanger, where the species was recorded for the first time in 1990. The Japanese wire weed Sargassum muticum was recorded on 26 of 36 sites, and was quite abundant on many of them. The method is well suited for mapping of sessile organisms in shallow waters, but is less applicable for recordings of mobile animals such as crustaceans

Rapid Coastal Survey in Norwegian Waters

European Marine Biological Symposium (EMBS 47), Arendal, 03.09.2012 - 07.09.201

Seasonal microbial processes in a high-latitude fjord (Kongsfjorden, Svalbard) : I. Heterotrophic bacteria, picoplankton and nanoflagellates

Temporal dynamics of the microbial food web in the Barents Sea and adjacent water masses in the European Arctic are to a large extent unknown. Seasonal variation in stocks and production rates of heterotrophic bacteria and phototrophic and heterotrophic picoplankton and nanoflagellates was investigated in the upper 50 m of the highlatitude Kongsfjorden, Svalbard, during six field campaigns between March and December 2006. Heterotrophic bacteria, picoplankton and nanoflagellates contributed to ecosystem structure and function in all seasons. Activity within the microbial food web peaked during spring bloom in April, parallel to low abundances of mesozooplankton. In the nutrient-limited post-bloom scenario, an efficient microbial loop, fuelled by dissolved organic carbon from abundant mesozooplankton feeding on phytoplankton and protozooplankton, facilitated maximum integrated primary production rates. A tight microbial food web consisting of heterotrophic bacteria and phototrophic and heterotrophic picoplankton and nanoflagellates was found in the stratified water masses encountered in July and September. Microbial stocks and rates were low but persistent under winter conditions. Seasonal comparisons of microbial biomass and production revealed that structure and function of the microbial food web were fundamentally different during the spring bloom when compared with other seasons. While the microbial food web was in a regenerative mode most of the time, during the spring bloom, a microbial transfer mode represented a trophic link for organic carbon in time and space. The microbial food web’s ability to fill different functional roles in periods dominated by new and regenerated production may enhance the ecological flexibility of pelagic ecosystems in the present era of climate change

Microbial processes in a high-latitude fjord (Kongsfjorden, Svalbard) : II. Ciliates and dinoflagellates

The composition and ecological role of ciliates and dinoflagellates were investigated at one station in Kongsfjorden, Svalbard, during six consecutive field campaigns between March and December 2006. Total ciliate and dinoflagellate abundance mirrored the seasonal progression of phytoplankton, peaking with 5.8 9 104 cells l-1 in April at an average chlorophyll a concentration of 10 lg l-1. Dinoflagellates were more abundant than ciliates, dominated by small athecates. Among ciliates, aloricate oligotrichs dominated the assemblage. A large fraction ([60%) of ciliates and dinoflagellates contained chloroplasts in spring and summer. The biomass of the purely heterotrophic fraction of the ciliate and dinoflagellate community (protozooplankton) was with 14 lg C l-1 highest in conjunction with the phytoplankton spring bloom in April. Growth experiments revealed similar specific growth rates for heterotrophic ciliates and dinoflagellates (\0–0.8 d-1). Food availability may have controlled the protozooplankton assemblage in winter, while copepods may have exerted a strong control during the post-bloom period. Calculations of the potential grazing rates of the protozooplankton indicated its ability to control or heavily impact the phytoplankton stocks at most times. The results show that ciliates and dinoflagellates were an important component of the pelagic food web in Kongsfjorden and need to be taken into account when discussing the fate of phytoplankton and biogeochemical cycling in Arctic marine ecosystems

Kartlegging av fremmede marine arter i Rogaland

The method Rapid Coastal Survey was applied in 36 marinas in the county of Rogaland during five days in august 2010. 27 introduced species were targeted in this investigation. No new species to Norway was found, but six species already established in Norway were observed at a number of sites. The ascidian Styela clava, native to northwest Pacific, was recorded at eleven sites in the county, and was most abundant at sites near Stavanger, where the species was recorded for the first time in 1990. The Japanese wire weed Sargassum muticum was recorded on 26 of 36 sites, and was quite abundant on many of them. The method is well suited for mapping of sessile organisms in shallow waters, but is less applicable for recordings of mobile animals such as crustaceans

Kartlegging av fremmede marine arter i Rogaland

The method Rapid Coastal Survey was applied in 36 marinas in the county of Rogaland during five days in august 2010. 27 introduced species were targeted in this investigation. No new species to Norway was found, but six species already established in Norway were observed at a number of sites. The ascidian Styela clava, native to northwest Pacific, was recorded at eleven sites in the county, and was most abundant at sites near Stavanger, where the species was recorded for the first time in 1990. The Japanese wire weed Sargassum muticum was recorded on 26 of 36 sites, and was quite abundant on many of them. The method is well suited for mapping of sessile organisms in shallow waters, but is less applicable for recordings of mobile animals such as crustaceans

Effects of small-scale turbulence on lower trophic levels under different nutrient conditions

Small-scale turbulence affects the pelagic food web and energy flow in marine systems and the impact is related to nutrient conditions and the assemblage of organisms present. We generated five levels of turbulence (2*10−9 to 1*10−4 W kg−1) in land-based mesocosms (volume 2.6 m3) with and without additional nutrients (31:16:1 Si:N:P μM) to asses the effect of small-scale turbulence on the lower part of the pelagic food web under different nutrient conditions. The ecological influence of nutrients and small-scale turbulence on lower trophic levels was quantified using multivariate statistics (RDA), where nutrients accounted for 31.8% of the observed biological variation, while 7.2% of the variation was explained by small-scale turbulence and its interaction with nutrients. Chlorophyll a, primary production rates, bacterial production rates and diatom and dinoflagellate abundance were positively correlated to turbulence, regardless of nutrient conditions. Abundance of autotrophic flagellates, total phytoplankton and bacteria were positively correlated to turbulence only when nutrients were added. Impact of small-scale turbulence was related to nutrient conditions, with implications for oligotrophic and eutrophic situations. The effect on community level was also different compared to single species level. Microbial processes drive biogeochemical cycles, and nutrient-controlled effects of small-scale turbulence on such processes are relevant to foresee altered carbon flow in marine systems