Degrading seagrass (Posidonia oceanica) ecosystems: a source of dissolved matter in the Mediterranean

Apostolaki, Eugenia T.; Holmer, Marianne; Marbà, Núria; Karakassis, Ioannis

doi:10.1007/s10750-010-0255-2

Cited by 29 publications

(18 citation statements)

References 51 publications

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“…As such, the remaining missing 12.6% of the initially incorporated 15 N label was most likely lost as DON. Consistent with a loss of DON was the small loss of DOC from the same experimental study (Oakes et al ), although the DO 13 C:DO 15 N ratio would have to be low (0.6 : 1.0) to account for all (12.6%) the missing 15 N. Similarly low benthic DOC:DON flux ratios have been measured in coastal sediments (Apostolaki et al ; Eyre et al ), and probably represent the preferential release of high‐molecular‐weight, low C : N compounds during early diagenesis (Burdige and Zheng ; Eyre and Ferguson ). MPB would provide a source of fresh organic matter, with high MPB biomass associated with high benthic DON fluxes (Cook et al ; Ferguson and Eyre ), and some of the DON may also have been released during grazing of MPB or viral lysis (Eyre and Ferguson ; Brussaard ).…”

Section: Discussionsupporting

confidence: 63%

Fate of microphytobenthos nitrogen in subtropical subtidal sediments: A ¹⁵ N pulse-chase study

2016

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Microphytobenthos (MPB) are an important nitrogen (N) sink in coastal systems, but little is known about the fate of this N after it has been assimilated. We used an in situ 15N pulse‐chase experiment in subtidal sands to follow the assimilation, trophic transfer, transformation, and flux pathways of MPB‐N over 33 d. Throughout the study MPB dominated 15N uptake, on average representing only 18.1% of the biomass but 63.9% of the 15N within 0–2 cm sediment. Following assimilation, 15N was rapidly transferred to deeper sediment, with 32.1% below 2 cm and 16.5% below 5 cm after 60 h. In contrast to MPB, bacteria represented 39.5% of sediment biomass but accounted for only up to 27.3% of assimilated 15N. Foraminifera accumulated and stored 15N more than bacteria; their contribution to the 15N remaining in 0–2 cm sediment at the end of the study was more than double their biomass contribution. Thirty‐three days after the 15N was assimilated by MPB 27% remained in the sediment, 16.5% had been effluxed as NO3−, 20.8% had been effluxed as NH4+, 20.7% had been effluxed as N2 and 15.1% was missing. Most (12.6%) of 15N label that was missing at the end of the study was probably lost as dissolved organic N (DON) fluxes. Of the 15N remaining in 0–2 cm sediment, 80.4% was in MPB, 2.7% in bacteria, 1% in foraminifera and the remaining 15.9% was uncharacterized. Overall there was little benthic trophic transfer with most of the MPB‐assimilated N remineralized over 33 d.

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Section: Discussionsupporting

confidence: 63%

Fate of microphytobenthos nitrogen in subtropical subtidal sediments: A ¹⁵ N pulse-chase study

2016

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“…Unfortunately, as no pH, A T and/ or DIC data were aquired for the sediment porewater during this study, it is impossible to assess the response of the sediment to pH changes in porewater and evaluate the contribution of this process to the observed ΔA T . A previous study in Saronikos Gulf has shown that under dark conditions DIC efflux from the sediment towards the water column takes place that is negatively related with DO suggesting mineralization processes (Apostolaki et al, 2010).…”

Section: Carbonate System Processes -Evidence Of Alkalinity Generationmentioning

confidence: 85%

Simulation of Coastal Processes affecting pH with Impacts on Carbon and Nutrient Biogeochemistry

et al. 2018

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Naturally occurring microbial decomposition of organic matter (OM) in coastal marine environments cause increased acidity in deeper layers similar or even exceeding the future predictions for global ocean acidification (OA). Experimental studies in coastal areas characterized by increased inputs of OM and nutrients, coping with intermittent hypoxic/anoxic conditions, provide better understanding of the mechanisms affecting nutrients and carbon biogeochemistry under the emerging effects of coastal pH decrease. Laboratory CO 2 -manipulated microcosm experiments were conducted using seawater and surface sediment collected from the deepest part of Elefsis Bay (Saronikos Gulf, Eastern Mediterranean) focusing to study the co-evolution of processes affected by the decline of dissolved oxygen and pH induced by (a) OM remineralization and (b) the future anthropogenic increase of atmospheric CO 2 . Under more acidified conditions, a significant increase of total alkalinity was observed partially attributed to the sedimentary carbonate dissolution and the reactive nitrogen species shift towards ammonium. Νitrate and nitrite decline, in parallel with ammonium increase, demonstrated a deceleration of ammonium oxidation processes along with decrease in nitrate production. The decreased DIN:DIP ratio, the prevalence of organic nutrient species against the inorganic ones, the observations of constrained DON degradation and nitrate production decline and the higher DOC concentrations revealed the possible inhibition of OM decomposition under lower pH values. Finally, our results highlight the need for detailed studies of the carbonate system in coastal areas dominated by hypoxic/anoxic conditions, accompanied by other biogeochemical parameters and properly designed experiments to elucidate the processes sequence or alterations due to pH reduction.

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“…Even though similarities in the genomes of many Bacteroidetes indicate that they have adopted the same life strategy, which is associated with particulate organic matter degradation (75), it remains unclear why in this study different Bacteroidetes groups were increased in abundance in different nutrient-enriched sites. We can only hypothesize that this may be related to the different origins of the alga-derived organic matter in the two sites, possibly due to the degradation of the macroalga Posidonia oceanica near the fish farm in Sitia (76). Another indication for macroalga degradation in Sitia comes from the increased abundance in this site of the Colwelliaceae, a group related to macroalga tissue decomposition (77).…”

Section: Discussionmentioning

confidence: 97%

The Pattern of Change in the Abundances of Specific Bacterioplankton Groups Is Consistent across Different Nutrient-Enriched Habitats in Crete

Fodelianakis

Papageorgiou

Pitta

et al. 2014

Appl Environ Microbiol

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A common source of disturbance for coastal aquatic habitats is nutrient enrichment through anthropogenic activities. Although the water column bacterioplankton communities in these environments have been characterized in some cases, changes in ␣-diversity and/or the abundances of specific taxonomic groups across enriched habitats remain unclear. Here, we investigated the bacterial community changes at three different nutrient-enriched and adjacent undisturbed habitats along the north coast of Crete, Greece: a fish farm, a closed bay within a town with low water renewal rates, and a city port where the level of nutrient enrichment and the trophic status of the habitat were different. Even though changes in ␣-diversity were different at each site, we observed across the sites a common change pattern accounting for most of the community variation for five of the most abundant bacterial groups: a decrease in the abundance of the Pelagibacteraceae and SAR86 and an increase in the abundance of the Alteromonadaceae, Rhodobacteraceae, and Cryomorphaceae in the impacted sites. The abundances of the groups that increased and decreased in the impacted sites were significantly correlated (positively and negatively, respectively) with the total heterotrophic bacterial counts and the concentrations of dissolved organic carbon and/or dissolved nitrogen and chlorophyll ␣, indicating that the common change pattern was associated with nutrient enrichment. Our results provide an in situ indication concerning the association of specific bacterioplankton groups with nutrient enrichment. These groups could potentially be used as indicators for nutrient enrichment if the pattern is confirmed over a broader spatial and temporal scale by future studies.

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Degrading seagrass (Posidonia oceanica) ecosystems: a source of dissolved matter in the Mediterranean

Cited by 29 publications

References 51 publications

Fate of microphytobenthos nitrogen in subtropical subtidal sediments: A ¹⁵ N pulse-chase study

Fate of microphytobenthos nitrogen in subtropical subtidal sediments: A ¹⁵ N pulse-chase study

Simulation of Coastal Processes affecting pH with Impacts on Carbon and Nutrient Biogeochemistry

The Pattern of Change in the Abundances of Specific Bacterioplankton Groups Is Consistent across Different Nutrient-Enriched Habitats in Crete

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Degrading seagrass (Posidonia oceanica) ecosystems: a source of dissolved matter in the Mediterranean

Cited by 29 publications

References 51 publications

Fate of microphytobenthos nitrogen in subtropical subtidal sediments: A 15 N pulse-chase study

Fate of microphytobenthos nitrogen in subtropical subtidal sediments: A 15 N pulse-chase study

Simulation of Coastal Processes affecting pH with Impacts on Carbon and Nutrient Biogeochemistry

The Pattern of Change in the Abundances of Specific Bacterioplankton Groups Is Consistent across Different Nutrient-Enriched Habitats in Crete

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Fate of microphytobenthos nitrogen in subtropical subtidal sediments: A ¹⁵ N pulse-chase study

Fate of microphytobenthos nitrogen in subtropical subtidal sediments: A ¹⁵ N pulse-chase study