Abstract Dissolved organic carbon (DOC) concentrations in lakes are changing globally, but little is known about potential ecosystem impacts.We evaluated the relationship between DOC and whole‐lake primary production arctic boreal lakes. Both light extinction (inhibits production) nutrient availability (stimulates positively nonlinearly related to concentration. These nonlinearities create a threshold concentration (4.8 mg L −1 ), below which DOC‐primary positive, above negative. varies...

We investigated productivity at the basal trophic level in 15 unproductive lakes a gradient ranging from clear‐water to brown‐water (humic) northern Sweden. Primary production and bacterial benthic pelagic habitats were measured estimate variation energy mobilization external sources (primary plus on allochthonous organic carbon) along gradient. Clear‐water dominated by autotrophic habitat, whereas humic heterotrophic habitat. Whole‐lake (benthic + pelagic) was negatively correlated...

We quantified the utilization of terrestrial organic matter (OM) in food web a humic lake by analyzing metabolism and consumers' stable isotopic (C, H, N) composition benthic pelagic habitats. Terrestrial OM inputs (3 g C m −2 d −1 ) to greatly exceeded autochthonous production mg lake. Heterotrophic bacterial growth (19 community respiration (115 were high relative algal photosynthesis predominantly (> 85%) supported both Consequently, fueled most (85%) total at base lake's (i.e., sum...

This study quantified new biomass production of algae and bacteria in both benthic pelagic habitats clear‐water lakes to contrast how carbon from the atmosphere terrestrial sources regulates whole‐lake metabolism. We studied four small unproductive subarctic northern Sweden during one summer season. The was calculated as sum autotrophic by heterotrophic using allochthonous organic (OC). Whole‐lake dominated habitat (86% ± 4% [mean SD]) primary (77% 9%). Still, fueled OC constituted a...

We studied 15 lakes in northern Sweden with respect to primary production and respiration benthic pelagic habitats. The were characterized by different concentrations of colored dissolved organic carbon (DOC) terrestrial origin, forming a gradient ranging from clear‐water brown‐water lakes. Primary decreased increased on whole‐lake scale along the increasing DOC. Thus, became more net heterotrophic, i.e., had lower ecosystem (NEP = gross – community respiration), DOC this change coincided...

Summary 1. Invasions of top predators may have strong cascading effects in ecosystems affecting both prey species abundance and lower trophic levels. A recently discussed factor that enhance invasion is climate change this context, we studied the an northern pike into a subarctic lake ecosystem formerly inhabited by native predator Arctic char its fish, ninespined stickleback. 2. Our study demonstrated fish community composition from system with as high densities sticklebacks to very low...

Natural climate solutions to change are recognised as a mechanism for drawing down carbon from the atmosphere. Together with geoengineering, this represents potential solution reducing anthropogenic dioxide (CO2) concentrations in atmosphere, which contributing global warming. The storage of marine sediments at land-sea interface continental shelves is globally significant process. These play crucial role by providing both sequestration and efficient burial, enabling systems serve effective...

We studied a small subarctic lake to assess the magnitude of winter respiration and organic carbon (OC) source for this respiration. The concentration stable isotopic composition (δ 13 C) dissolved inorganic (DIC) accumulating in water under ice was analyzed over one (7 months). DIC increased δ C decreased time, with greatest changes at bottom. Winter 26% annual lake. Keeling plot analysis demonstrated that respired varied spatially, high values occurring shallow (2.5 m, 221.7‰%) compared...

Abstract Gross primary production (GPP) is a fundamental ecosystem process that sequesters carbon dioxide (CO 2 ) and forms the resource base for higher trophic levels. Still, relative contribution of different controls on GPP at whole-ecosystem scale far from resolved. Here we show, by manipulating CO concentrations in large-scale experimental pond ecosystems, availability key driver GPP. This result suggests need to reformulate past conceptual models describing lake productivity include...

Abstract Benthic gross primary production (GPP) is often the most important part of aquatic food webs in northern lakes, which are gradually warming and receiving increased terrestrial colored dissolved organic carbon loadings due to global change. Yet, measurements benthic GPP fairly uncommon, methods unit dimensions unstandardized rarely compared. In this study, we measured 27 headwater lakes from three regions Sweden analyzed potential constraining drivers z rates at discrete depths...

Abstract We tested interactive effects of warming (+2°C) and browning on periphyton accrual pigment composition when grown a synthetic substrate (plastic strips) in the euphotic zone 16 experimental ponds. found that increased colored dissolved organic matter (cDOM) associated nutrients alone, or combination with warming, resulted substantially enhanced biomass periphyton, comparatively smaller increase phytoplankton. This illustrates is capable using cDOM, by this may affect nutrient...

We monitored the hatching frequencies and clutch sizes of Eurytemora affinis, environmental variables in Gulf Bothnia, between May October 2003. tested hypothesis that frequency copepod would be negatively affected during time periods with high diatom concentrations. Results from two stations showed significant differences different sampling occasions, lowest observed spring bloom. The reverse was true for size, highest average egg number These results were not correlated to ambient...

Rivers transport large amounts of allochthonous organic matter (OM) to the ocean every year, but there are still fundamental gaps in how OM is processed marine environment. Here, we estimated relative contribution (allochthony) biomass benthic and pelagic consumers a shallow coastal ecosystem northern Baltic Sea. We used deuterium as tracer allochthony assessed both temporal variation (monthly from May August) spatial (within outside river plume). found variability space time across species,...

Abstract Global change affects gross primary production (GPP) in benthic and pelagic habitats of northern lakes by influencing catchment characteristics lake water biogeochemistry. However, how changes key environmental drivers manifest impact total (i.e., + pelagic) GPP the partitioning between represented share ( autotrophic structuring ) is unclear. Using a dataset from 26 shallow located across Arctic, subarctic, boreal Sweden, we investigate properties (air temperature, land cover,...

Global change impacts important environmental drivers for pelagic gross primary production (GPP) in northern lakes, such as temperature, light, nutrient, and inorganic carbon availability. Separate and/or synergistic of these on GPP remain largely unresolved. Here, we assess key by combining detailed depth profiles summer with climatic data across 45 small shallow lakes Sweden (20 boreal, 6 subarctic, 19 arctic lakes). We found that was strongest associated lake water temperatures, dioxide...

We carried out a set of experiments in small clear-water lake northern Sweden during summer 2010 to assess the effect organic C (OC) released from epipelic algae on pelagic bacterial production (BP). The release rate OC (dissolved and particulate) was ∼45.4 ng m−2 h−1. Bacterioplankton uptake dissolved P-limited, primary (PP) colimited by N P. Pelagic BP (3.2 ± 6 µg L−1 h−1) exceeded PP (0.012 0.008 h−1). higher water contact with sediments growing their surface than separated sediments....

Abstract Coastal eutrophication due to excessive anthropogenic nutrient loading is a major threat worldwide, and especially in estuaries semi‐enclosed waterbodies, like the brackish Baltic Sea. In addition, coastal waters may become darker (coastal darkening) increased input of colored compounds from terrestrial run‐off sediment resuspension. Still, effects darkening on food web responses are unknown. mesocosm experiment with benthic pelagic habitats, we manipulated loading, presence fish...

Virus-bacterium interactions were investigated in the pelagic and benthic habitats a set of lakes along an altitudinal gradient subarctic northern Sweden. Viral bacterial abundances showed significant variation between lakes, with highest microbial recorded high-altitude lake [993 m above sea level (a.s.l.)], whereas found low-altitude (270 a.s.l.). In habitat, there was also distinct difference summer-autumn winter sampling occasion. A positive relationship noted viruses bacteria both...

Abstract Gross primary production (GPP) by benthic microalgae growing on soft sediments is an important contributor to lake productivity in many lakes world‐wide. As have access nutrients the sediment they been regarded as primarily controlled light, while role of CO 2 a limiting factor for GPP ecosystems largely unknown. In this study, we experimentally tested limitation collecting littoral surface sediments, with associated microalgae, from typical boreal lake. Intact cores were incubated...