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Nitrogen fixed by cyanobacteria is utilized by deposit-feeders.

Karlson AM, Gorokhova E, Elmgren R - PLoS ONE (2014)

Bottom Line: We also expected the settled cyanobacteria with their associated microheterotrophic community and relatively high nitrogen content to increase the isotopic niche area, trophic diversity and dietary divergence between individuals (estimated as the nearest neighbour distance) in the benthic fauna after the bloom.The three surface-feeding species (Monoporeia affinis, Macoma balthica and Marenzelleria arctia) showed significantly lower δ(15)N values after the bloom, while the sub-surface feeder Pontoporeia femorata did not.The effect of the bloom on isotopic niche varied greatly between stations; populations which increased niche area after the bloom had better body condition than populations with reduced niche, regardless of species.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Environmental Science, Stockholm University, Stockholm, Sweden.

ABSTRACT
Benthic communities below the photic zone depend for food on allochthonous organic matter derived from seasonal phytoplankton blooms. In the Baltic Sea, the spring diatom bloom is considered the most important input of organic matter, whereas the contribution of the summer bloom dominated by diazotrophic cyanobacteria is less understood. The possible increase in cyanobacteria blooms as a consequence of eutrophication and climate change calls for evaluation of cyanobacteria effects on benthic community functioning and productivity. Here, we examine utilization of cyanobacterial nitrogen by deposit-feeding benthic macrofauna following a cyanobacteria bloom at three stations during two consecutive years and link these changes to isotopic niche and variations in body condition (assayed as C:N ratio) of the animals. Since nitrogen-fixing cyanobacteria have δ(15)N close to -2‰, we expected the δ(15)N in the deposit-feeders to decrease after the bloom if their assimilation of cyanobacteria-derived nitrogen was substantial. We also expected the settled cyanobacteria with their associated microheterotrophic community and relatively high nitrogen content to increase the isotopic niche area, trophic diversity and dietary divergence between individuals (estimated as the nearest neighbour distance) in the benthic fauna after the bloom. The three surface-feeding species (Monoporeia affinis, Macoma balthica and Marenzelleria arctia) showed significantly lower δ(15)N values after the bloom, while the sub-surface feeder Pontoporeia femorata did not. The effect of the bloom on isotopic niche varied greatly between stations; populations which increased niche area after the bloom had better body condition than populations with reduced niche, regardless of species. Thus, cyanobacterial nitrogen is efficiently integrated into the benthic food webs in the Baltic, with likely consequences for their functioning, secondary production, transfer efficiency, trophic interactions, and intra- and interspecific competition.

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Sampling occasions in relation bloom.Cyanobacteria bloom development in 2009 and 2010 at stn B1 (near sampling stations Håldämman and Uttervik), dotted line, and stn H3 (close to stn Mörkö), solid line. The X-axis is scaled for Julian days and benthos sampling dates are indicated by arrows. See text for the description of bloom composition. In 2010, stn Mörkö was sampled only in late June and September.
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pone-0104460-g001: Sampling occasions in relation bloom.Cyanobacteria bloom development in 2009 and 2010 at stn B1 (near sampling stations Håldämman and Uttervik), dotted line, and stn H3 (close to stn Mörkö), solid line. The X-axis is scaled for Julian days and benthos sampling dates are indicated by arrows. See text for the description of bloom composition. In 2010, stn Mörkö was sampled only in late June and September.

Mentions: We sampled sediment and deposit-feeding macrofauna at three coastal stations (stn) in the north-western Baltic proper (Figure 1); Håldämman (30 m bottom depth, 58°49′18 N, 17°34′58 E), Uttervik (20 m, 58°50′58 N, 17°32′77 E) and Mörkö (23 m, 58°54′13 N, 17°42′45 E). The sampling was scheduled around the cyanobacteria blooms in 2009 (May 26, June 2, August 13 and September 21) and 2010 (June 7, June 28 and- September 23). Stations Håldämman and Uttervik are located close (1 and 5 km, respectively) to the phytoplankton monitoring stn B1 (58°48′28 N, 17°37′60 E; Swedish National Marine Monitoring Program, data publicly available from www.smhi.se) and stn Mörkö right by the phytoplankton stn H3 (58°56′04 N, 17°43′81 E, Himmerfjärden Eutrophication study), 14 km from stn B1. No specific permission is required for sampling invertebrates in the Baltic Sea and the field studies did not involve any endangered or protected species. Figure 1 shows sampling schedule and cyanobacteria bloom development at both monitoring stations in 2009 and 2010.


Nitrogen fixed by cyanobacteria is utilized by deposit-feeders.

Karlson AM, Gorokhova E, Elmgren R - PLoS ONE (2014)

Sampling occasions in relation bloom.Cyanobacteria bloom development in 2009 and 2010 at stn B1 (near sampling stations Håldämman and Uttervik), dotted line, and stn H3 (close to stn Mörkö), solid line. The X-axis is scaled for Julian days and benthos sampling dates are indicated by arrows. See text for the description of bloom composition. In 2010, stn Mörkö was sampled only in late June and September.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4126700&req=5

pone-0104460-g001: Sampling occasions in relation bloom.Cyanobacteria bloom development in 2009 and 2010 at stn B1 (near sampling stations Håldämman and Uttervik), dotted line, and stn H3 (close to stn Mörkö), solid line. The X-axis is scaled for Julian days and benthos sampling dates are indicated by arrows. See text for the description of bloom composition. In 2010, stn Mörkö was sampled only in late June and September.
Mentions: We sampled sediment and deposit-feeding macrofauna at three coastal stations (stn) in the north-western Baltic proper (Figure 1); Håldämman (30 m bottom depth, 58°49′18 N, 17°34′58 E), Uttervik (20 m, 58°50′58 N, 17°32′77 E) and Mörkö (23 m, 58°54′13 N, 17°42′45 E). The sampling was scheduled around the cyanobacteria blooms in 2009 (May 26, June 2, August 13 and September 21) and 2010 (June 7, June 28 and- September 23). Stations Håldämman and Uttervik are located close (1 and 5 km, respectively) to the phytoplankton monitoring stn B1 (58°48′28 N, 17°37′60 E; Swedish National Marine Monitoring Program, data publicly available from www.smhi.se) and stn Mörkö right by the phytoplankton stn H3 (58°56′04 N, 17°43′81 E, Himmerfjärden Eutrophication study), 14 km from stn B1. No specific permission is required for sampling invertebrates in the Baltic Sea and the field studies did not involve any endangered or protected species. Figure 1 shows sampling schedule and cyanobacteria bloom development at both monitoring stations in 2009 and 2010.

Bottom Line: We also expected the settled cyanobacteria with their associated microheterotrophic community and relatively high nitrogen content to increase the isotopic niche area, trophic diversity and dietary divergence between individuals (estimated as the nearest neighbour distance) in the benthic fauna after the bloom.The three surface-feeding species (Monoporeia affinis, Macoma balthica and Marenzelleria arctia) showed significantly lower δ(15)N values after the bloom, while the sub-surface feeder Pontoporeia femorata did not.The effect of the bloom on isotopic niche varied greatly between stations; populations which increased niche area after the bloom had better body condition than populations with reduced niche, regardless of species.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Environmental Science, Stockholm University, Stockholm, Sweden.

ABSTRACT
Benthic communities below the photic zone depend for food on allochthonous organic matter derived from seasonal phytoplankton blooms. In the Baltic Sea, the spring diatom bloom is considered the most important input of organic matter, whereas the contribution of the summer bloom dominated by diazotrophic cyanobacteria is less understood. The possible increase in cyanobacteria blooms as a consequence of eutrophication and climate change calls for evaluation of cyanobacteria effects on benthic community functioning and productivity. Here, we examine utilization of cyanobacterial nitrogen by deposit-feeding benthic macrofauna following a cyanobacteria bloom at three stations during two consecutive years and link these changes to isotopic niche and variations in body condition (assayed as C:N ratio) of the animals. Since nitrogen-fixing cyanobacteria have δ(15)N close to -2‰, we expected the δ(15)N in the deposit-feeders to decrease after the bloom if their assimilation of cyanobacteria-derived nitrogen was substantial. We also expected the settled cyanobacteria with their associated microheterotrophic community and relatively high nitrogen content to increase the isotopic niche area, trophic diversity and dietary divergence between individuals (estimated as the nearest neighbour distance) in the benthic fauna after the bloom. The three surface-feeding species (Monoporeia affinis, Macoma balthica and Marenzelleria arctia) showed significantly lower δ(15)N values after the bloom, while the sub-surface feeder Pontoporeia femorata did not. The effect of the bloom on isotopic niche varied greatly between stations; populations which increased niche area after the bloom had better body condition than populations with reduced niche, regardless of species. Thus, cyanobacterial nitrogen is efficiently integrated into the benthic food webs in the Baltic, with likely consequences for their functioning, secondary production, transfer efficiency, trophic interactions, and intra- and interspecific competition.

Show MeSH
Related in: MedlinePlus