Warming but not increased terrestrial doc has negative effects on fish recruitment
(English)Manuscript (preprint) (Other academic)
Water temperature and export of terrestrial dissolved organic carbon (DOC) to recipient aquatic ecosystems have strong impacts on ecosystem productivity. Increased DOC concentration causing brownification of water is argued to reduce fish production by decreasing light availability for autotrophic production. On the other hand, higher temperatures have been shown to correlate positively with fish recruitment. This increase has been related to increased growth rates and survival of young-of-the-year (YOY) fish with warming. However, whether or not increased temperature results in higher growth depends on resource availability, suggesting a relationship between individual gain and recruitment mediated via the interplay between resource production and temperature. In a replicated, large scale experimental pond ecosystem, we tested the effects of increased temperature (+3oC) and terrestrial DOC concentrations (+4 mg/l) on recruitment (size, density and biomass) of three-spined sticklebacks over one growth season. Gross primary production (GPP) was similar between treatments, whereas zooplankton and benthic invertebrate biomass were negatively affected by increased temperature and if any higher at increased DOC levels. Increased temperature had no effect on individual size but negative effects on body condition and recruitment of YOY sticklebacks, while increased DOC concentration had no effect on recruitment. No positive effect of temperature increase on GPP and decreased resource levels in combination with higher metabolic costs, are suggested to increase starvation mortality and to be the main mechanism behind observed negative effects of warming on recruitment. Based on our results, we suggest that climate change may, counter intuitively, have negative effects on fish recruitment due to decreased carrying capacity of nursery habitats as a consequence of increased energy requirements in juvenile fish in relation to the net effects on resource production and ecosystem productivity.
Temperature, metabolism, search efficiency, dissolved organic carbon (DOC), Gross primary production (GPP), somatic growth, macroinvertebrates
IdentifiersURN: urn:nbn:se:umu:diva-127938OAI: oai:DiVA.org:umu-127938DiVA: diva2:1048299
FunderThe Kempe FoundationsSwedish Research Council for Environment, Agricultural Sciences and Spatial Planning, 621-2011-3908Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGE