Effects of changing phytoplankton species composition on carbon and nitrogen uptake in benthic invertebrates

Hedberg, Per; Albert, Séréna; Nascimento, Francisco J. A.; Winder, Monika

doi:10.1002/lno.11617

Cited by 15 publications

(28 citation statements)

References 61 publications

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“…The hypoxic area is defined as the annual maximum extent of areas with oxygen concentration < 2 mg 02 l -1 and is given for the whole basins on a logarithmic scale (f). Respiratory quotient for benthic fauna g O2 mg C -1 0.00266 1 mol mol -1 (Brey, 2001) *Based on stoichiometric ratios measured from Baltic Sea benthic fauna (Carman and Cederwall, 2001;Cederwall and Jermakovs, 1999;Hedberg et al, 2020;Kahma et al, 2020;Kumblad and Bradshaw, 2008;Lehtonen, 1996;S. M äkelin & A. Villnäs, unpubl.…”

Section: Discussionmentioning

confidence: 99%

Large-scale effects of benthic fauna on carbon, nitrogen, and phosphorus dynamics in the Baltic Sea

Ehrnsten

Savchuk

Gustafsson

2022

Preprint

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Abstract. Even though the effects of benthic fauna on aquatic biogeochemistry have been long recognized, few studies have addressed the combined effects of animal bioturbation and metabolism on ecosystem–level carbon and nutrient dynamics. Here we merge a model of benthic fauna (BMM) into a physical–biogeochemical ecosystem model (BALTSEM) to study the long–term and large–scale effects of benthic fauna on nutrient and carbon cycling in the Baltic Sea. We include both the direct effects of faunal growth and metabolism and the indirect effects of its bioturbating activities on biogeochemical fluxes of and transformations between organic and inorganic forms of carbon (C), nitrogen (N), phosphorus (P) and oxygen (O). Analyses of simulation results from the Baltic Proper and Gulf of Riga indicate that benthic fauna makes up a small portion of seafloor organic stocks, but contributes considerably to benthic–pelagic fluxes of inorganic C, N and P through its metabolism. Results also suggest that the relative contribution of fauna to mineralisation of sediment organic matter increases with increasing nutrient loads. Further, bioturbation decreases benthic denitrification and increases P retention in sediments, the latter having far–reaching consequences throughout the ecosystem. Reduced benthic–pelagic P fluxes lead to a reduction of N fixation and primary production, lower organic matter sedimentation fluxes and thereby generally lower benthic stocks and fluxes of C, N and P. This chain of indirect effects overrides the direct effects of faunal respiration, excretion and bioturbation. Due to large uncertainties related to parameterization of benthic processes, we consider this modelling study a first step towards disentangling the complex large–scale effects of benthic fauna on biogeochemical cycling.

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Section: Discussionmentioning

confidence: 99%

Large-scale effects of benthic fauna on carbon, nitrogen, and phosphorus dynamics in the Baltic Sea

Ehrnsten

Savchuk

Gustafsson

2022

Preprint

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“…Yet, not all taxa display a similar response to spring bloom settling, which points to the existence of different strategies in resource utilization 2 , 17 , 21 , 41 . Later in the summer, nitrogen-fixing cyanobacteria can also contribute to OM export towards the sediment, and support benthic secondary production to some extent 6 , 26 , 42 , 43 . Radiotracer experiments have documented that meiofauna can utilize both diatom- 44 and cyanobacteria-derived OM 26 , albeit with substantial differences in assimilation rates and growth benefits 27 .…”

Section: Discussionmentioning

confidence: 99%

“…Culture conditions are described in Hedberg et al . 43 . After 6 days, the phytoplankton material in each culture was rinsed 3 times with sterile artificial seawater and concentrated in a slurry.…”

Section: Methodsmentioning

confidence: 99%

Phytoplankton settling quality has a subtle but significant effect on sediment microeukaryotic and bacterial communities

Albert

Hedberg

Motwani

et al. 2021

Sci Rep

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In coastal aphotic sediments, organic matter (OM) input from phytoplankton is the primary food resource for benthic organisms. Current observations from temperate ecosystems like the Baltic Sea report a decline in spring bloom diatoms, while summer cyanobacteria blooms are becoming more frequent and intense. These climate-driven changes in phytoplankton communities may in turn have important consequences for benthic biodiversity and ecosystem functions, but such questions are not yet sufficiently explored experimentally. Here, in a 4-week experiment, we investigated the response of microeukaryotic and bacterial communities to different types of OM inputs comprising five ratios of two common phytoplankton species in the Baltic Sea, the diatom Skeletonema marinoi and filamentous cyanobacterium Nodularia spumigena. Metabarcoding analyses on 16S and 18S ribosomal RNA (rRNA) at the experiment termination revealed subtle but significant changes in diversity and community composition of microeukaryotes in response to settling OM quality. Sediment bacteria were less affected, although we observed a clear effect on denitrification gene expression (nirS and nosZ), which was positively correlated with increasing proportions of cyanobacteria. Altogether, these results suggest that future changes in OM input to the seafloor may have important effects on both the composition and function of microbenthic communities.

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“…M . balthica is known to consume both diatoms and cyanobacteria, but appears to prefer the former over the latter [ 63 , 64 ]. Additionally, M .…”

Section: Introductionmentioning

confidence: 99%

“…With these knowledge gaps in mind, we performed an experiment where two groups of the Baltic clam M . balthica from differing levels of physical forcing exposure (sheltered or exposed) were fed two common species of phytoplankton that are known to be part of their natural diet: the cyanobacteria Nodularia spumigena and the diatom Skeletonema marinoi [ 64 ]. First, we aimed to confirm the presence of phytoplankton DNA in the digestive tract of M .…”

Section: Introductionmentioning

confidence: 99%

Molecular diet analysis enables detection of diatom and cyanobacteria DNA in the gut of Macoma balthica

et al. 2022

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Detritivores are essential to nutrient cycling, but are often neglected in trophic networks, due to difficulties with determining their diet. DNA analysis of gut contents shows promise of trophic link discrimination, but many unknown factors limit its usefulness. For example, DNA can be rapidly broken down, especially by digestion processes, and DNA provides only a snapshot of the gut contents at a specific time. Few studies have been performed on the length of time that prey DNA can be detected in consumer guts, and none so far using benthic detritivores. Eutrophication, along with climate change, is altering the phytoplankton communities in aquatic ecosystems, on which benthic detritivores in aphotic soft sediments depend. Nutrient-poor cyanobacteria blooms are increasing in frequency, duration, and magnitude in many water bodies, while nutrient-rich diatom spring blooms are shrinking in duration and magnitude, creating potential changes in diet of benthic detritivores. We performed an experiment to identify the taxonomy and quantify the abundance of phytoplankton DNA fragments on bivalve gut contents, and how long these fragments can be detected after consumption in the Baltic Sea clam Macoma balthica. Two common species of phytoplankton (the cyanobacteria Nodularia spumigena or the diatom Skeletonema marinoi) were fed to M. balthica from two regions (from the northern and southern Stockholm archipelago). After removing the food source, M. balthica gut contents were sampled every 24 hours for seven days to determine the number of 23S rRNA phytoplankton DNA copies and when the phytoplankton DNA could no longer be detected by quantitative PCR. We found no differences in diatom 18S rRNA gene fragments of the clams by region, but the southern clams showed significantly more cyanobacteria 16S rRNA gene fragments in their guts than the northern clams. Interestingly, the cyanobacteria and diatom DNA fragments were still detectable by qPCR in the guts of M. balthica one week after removal from its food source. However, DNA metabarcoding of the 23S rRNA phytoplankton gene found in the clam guts showed that added food (i.e. N. spumigena and S. marinoi) did not make up a majority of the detected diet. Our results suggest that these detritivorous clams therefore do not react as quickly as previously thought to fresh organic matter inputs, with other phytoplankton than large diatoms and cyanobacteria constituting the majority of their diet. This experiment demonstrates the viability of using molecular methods to determine feeding of detritivores, but further studies investigating how prey DNA signals can change over time in benthic detritivores will be needed before this method can be widely applicable to both models of ecological functions and conservation policy.

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Effects of changing phytoplankton species composition on carbon and nitrogen uptake in benthic invertebrates

Cited by 15 publications

References 61 publications

Large-scale effects of benthic fauna on carbon, nitrogen, and phosphorus dynamics in the Baltic Sea

Large-scale effects of benthic fauna on carbon, nitrogen, and phosphorus dynamics in the Baltic Sea

Phytoplankton settling quality has a subtle but significant effect on sediment microeukaryotic and bacterial communities

Molecular diet analysis enables detection of diatom and cyanobacteria DNA in the gut of Macoma balthica

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