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Gérard Blanchard - One of the best experts on this subject based on the ideXlab platform.
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Food sources used by sediment meiofauna in an intertidal Zostera noltii Seagrass Bed: a seasonal stable isotope study
Marine Biology, 2012Co-Authors: Benoit Lebreton, Pierre Richard, Robert Galois, Gilles Radenac, Amel Brahmia, Géraldine Colli, Marig Grouazel, Cyril André, Gaël Guillou, Gérard BlanchardAbstract:In an intertidal Zostera noltii Hornem. Seagrass Bed, food sources used by sediment meiofauna were determined seasonally by comparing stable isotope signatures (δ13C, δ15N) of sources with those of nematodes and copepods. Proportions of different carbon sources used by consumers were estimated using the SIAR mixing model on δ13C values. Contrary to δ15N values, food source mean δ13C values encompassed a large range, from -22.1‰ (suspended particulate organic matter) to -10.0‰ (Z. noltii roots). δ13C values of copepods (from -22.3 to -12.3‰) showed that they use many food sources (benthic and phytoplanktonic microalgae, Z. noltii matter). Nematode δ13C values ranged from -14.6 to -11.4‰, indicating a strong role of microphytobenthos and/or Z. noltii matter as carbon sources. The difference of food source uses between copepods and nematodes is discussed in the light of source accessibility and availability.
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Trophic importance of diatoms in an intertidal Zostera noltii Seagrass Bed: Evidence from stable isotope and fatty acid analyses
Estuarine Coastal and Shelf Science, 2011Co-Authors: Benoit Lebreton, Pierre Richard, Robert Galois, Gilles Radenac, Gaël Guillou, Camille Pfléger, Françoise Mornet, Gérard BlanchardAbstract:A current predominant paradigm emphasizes the role of epiphytic algae for invertebrates in most of Seagrass food webs. However, in some intertidal Zostera noltii Beds, epiphyte biomass is very low compared to microphytobenthos and Seagrass biomasses. We assessed the role of microphytobenthos in a temperate intertidal Z. noltii Bed by combining stable isotope and fatty acid (FA) analyses on primary producers, composite sources — suspended particulate organic matter (SPOM) and sediment surface organic matter (SSOM) — and the main macrofaunal consumers. Z. noltii showed high δ 13 C (-9.9‰) and high 18:2(n-6) and 18:3(n-3) contents. Microphytobenthos was slightly more 13 C-depleted (-15.4‰) and had high levels of diatom markers: 14:0, 16:1(n-7)c, 20:5(n-3). Low mean δ 13 C (-22.0‰) and large amounts of diatom and bacteria (18:1(n-7)c) markers indicated that SPOM was mainly composed of a mixture of fresh and decayed pelagic diatoms. Higher mean δ 13 C (-17.9 ‰) and high amounts of diatom FAs were found in SSOM, showing that microphytobenthic diatoms dominate. Very low percentages of 18:2(n-6) and 18:3(n-3) in consumers indicated a low contribution of Z. noltii material to their diets. Grazers, deposit and suspension-deposit feeders had δ 13 C close to microphytobenthos and high levels of diatom FAs, confirming that microphytobenthos represented the main part of their diet. Lower δ 13 C and higher amounts of flagellate FAs – 22:6(n-3) and 16:4(n-3) – in suspension feeders indicated that their diet resulted from a mixture of SPOM and microphytobenthos. These results demonstrate that invertebrates do not consume high amounts of Seagrass and highlight the main role of benthic diatoms in this intertidal Seagrass Bed.
Benoit Lebreton - One of the best experts on this subject based on the ideXlab platform.
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food sources used by sediment meiofauna in an intertidal zostera noltii Seagrass Bed a seasonal stable isotope study
Marine Biology, 2012Co-Authors: Benoit Lebreton, Pierre Richard, Robert Galois, Gilles Radenac, Amel Brahmia, Géraldine Colli, Marig Grouazel, Cyril André, Gaël Guillou, Gerard F BlanchardAbstract:In an intertidal Zostera noltii Hornem Seagrass Bed, food sources used by sediment meiofauna were determined seasonally by comparing stable isotope signatures (δ13C, δ15N) of sources with those of nematodes and copepods. Proportions of different carbon sources used by consumers were estimated using the SIAR mixing model on δ13C values. Contrary to δ15N values, food source mean δ13C values encompassed a large range, from −22.1 ‰ (suspended particulate organic matter) to −10.0 ‰ (Z. noltii roots). δ13C values of copepods (from −22.3 to −12.3 ‰) showed that they use many food sources (benthic and phytoplanktonic microalgae, Z. noltii matter). Nematode δ13C values ranged from −14.6 to −11.4 ‰, indicating a strong role of microphytobenthos and/or Z. noltii matter as carbon sources. The difference of food source uses between copepods and nematodes is discussed in light of source accessibility and availability.
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Food sources used by sediment meiofauna in an intertidal Zostera noltii Seagrass Bed: a seasonal stable isotope study
Marine Biology, 2012Co-Authors: Benoit Lebreton, Pierre Richard, Robert Galois, Gilles Radenac, Amel Brahmia, Géraldine Colli, Marig Grouazel, Cyril André, Gaël Guillou, Gérard BlanchardAbstract:In an intertidal Zostera noltii Hornem. Seagrass Bed, food sources used by sediment meiofauna were determined seasonally by comparing stable isotope signatures (δ13C, δ15N) of sources with those of nematodes and copepods. Proportions of different carbon sources used by consumers were estimated using the SIAR mixing model on δ13C values. Contrary to δ15N values, food source mean δ13C values encompassed a large range, from -22.1‰ (suspended particulate organic matter) to -10.0‰ (Z. noltii roots). δ13C values of copepods (from -22.3 to -12.3‰) showed that they use many food sources (benthic and phytoplanktonic microalgae, Z. noltii matter). Nematode δ13C values ranged from -14.6 to -11.4‰, indicating a strong role of microphytobenthos and/or Z. noltii matter as carbon sources. The difference of food source uses between copepods and nematodes is discussed in the light of source accessibility and availability.
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Trophic importance of diatoms in an intertidal Zostera noltii Seagrass Bed: Evidence from stable isotope and fatty acid analyses
Estuarine Coastal and Shelf Science, 2011Co-Authors: Benoit Lebreton, Pierre Richard, Robert Galois, Gilles Radenac, Gaël Guillou, Camille Pfléger, Françoise Mornet, Gérard BlanchardAbstract:A current predominant paradigm emphasizes the role of epiphytic algae for invertebrates in most of Seagrass food webs. However, in some intertidal Zostera noltii Beds, epiphyte biomass is very low compared to microphytobenthos and Seagrass biomasses. We assessed the role of microphytobenthos in a temperate intertidal Z. noltii Bed by combining stable isotope and fatty acid (FA) analyses on primary producers, composite sources — suspended particulate organic matter (SPOM) and sediment surface organic matter (SSOM) — and the main macrofaunal consumers. Z. noltii showed high δ 13 C (-9.9‰) and high 18:2(n-6) and 18:3(n-3) contents. Microphytobenthos was slightly more 13 C-depleted (-15.4‰) and had high levels of diatom markers: 14:0, 16:1(n-7)c, 20:5(n-3). Low mean δ 13 C (-22.0‰) and large amounts of diatom and bacteria (18:1(n-7)c) markers indicated that SPOM was mainly composed of a mixture of fresh and decayed pelagic diatoms. Higher mean δ 13 C (-17.9 ‰) and high amounts of diatom FAs were found in SSOM, showing that microphytobenthic diatoms dominate. Very low percentages of 18:2(n-6) and 18:3(n-3) in consumers indicated a low contribution of Z. noltii material to their diets. Grazers, deposit and suspension-deposit feeders had δ 13 C close to microphytobenthos and high levels of diatom FAs, confirming that microphytobenthos represented the main part of their diet. Lower δ 13 C and higher amounts of flagellate FAs – 22:6(n-3) and 16:4(n-3) – in suspension feeders indicated that their diet resulted from a mixture of SPOM and microphytobenthos. These results demonstrate that invertebrates do not consume high amounts of Seagrass and highlight the main role of benthic diatoms in this intertidal Seagrass Bed.
Jun Shoji - One of the best experts on this subject based on the ideXlab platform.
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day night change in fish community structure in a Seagrass Bed in subarctic waters
Fisheries Science, 2018Co-Authors: Susumu Chiba, Hiroki Tanaka, Takashi Yusa, Jun ShojiAbstract:The day–night change in fish community structure over a year was examined in a Seagrass Bed in Lake Notoro, Hokkaido, northern Japan, to examine nocturnal increases in predation risk. This Seagrass Bed has previously been considered a predation refuge for juvenile and small-sized fishes. Species richness, abundance and biomass of piscivorous fishes during nighttime were higher than those during daytime on all sample dates surveyed (May, August and November 2013), indicating an increase in predation risk for juvenile and small-sized fishes during nighttime. The mean biomass-weighted trophic level of fish communities in the Seagrass Bed was also higher at night than in the day. The piscivorous fishes collected in the Seagrass Bed during the night included important fishery species. These may obtain energy through nocturnal feeding in the Seagrass Bed. Therefore, the function of Seagrass Beds as fish habitats should be re-evaluated by considering two possible characteristics contributing to fishery production: as a daytime predation refuge for juvenile and small-sized fishes, and as a nighttime foraging ground for piscivorous fishes.
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Day–night change in fish community structure in a Seagrass Bed in subarctic waters
Fisheries Science, 2018Co-Authors: Hiroki Tanaka, Susumu Chiba, Takashi Yusa, Jun ShojiAbstract:The day–night change in fish community structure over a year was examined in a Seagrass Bed in Lake Notoro, Hokkaido, northern Japan, to examine nocturnal increases in predation risk. This Seagrass Bed has previously been considered a predation refuge for juvenile and small-sized fishes. Species richness, abundance and biomass of piscivorous fishes during nighttime were higher than those during daytime on all sample dates surveyed (May, August and November 2013), indicating an increase in predation risk for juvenile and small-sized fishes during nighttime. The mean biomass-weighted trophic level of fish communities in the Seagrass Bed was also higher at night than in the day. The piscivorous fishes collected in the Seagrass Bed during the night included important fishery species. These may obtain energy through nocturnal feeding in the Seagrass Bed. Therefore, the function of Seagrass Beds as fish habitats should be re-evaluated by considering two possible characteristics contributing to fishery production: as a daytime predation refuge for juvenile and small-sized fishes, and as a nighttime foraging ground for piscivorous fishes.
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increase in predation risk and trophic level induced by nocturnal visits of piscivorous fishes in a temperate Seagrass Bed
Scientific Reports, 2017Co-Authors: Jun Shoji, Hiromichi Mitamura, Kotaro Ichikawa, Hikari Kinoshita, Nobuaki AraiAbstract:The majority of surveys on food webs of aquatic ecosystems have been conducted during the day owning to difficulties in sampling animals at night. In this study, to examine diurnal changes in predator-prey interactions in a temperate Seagrass Zostera marina Bed, a quantitative day/night survey of fish, the dominant animal community, coupled with acoustic telemetry of their predators, was conducted. The number of species, abundance, and biomass of piscivorous predators and mean trophic level during the night were significantly higher than those in the day in all seasons. Analysis of the stomach contents of 182 piscivorous predators showed that no fish predation occurred during the day whereas predation occurred during the night in winter, spring, and summer. Acoustic telemetry demonstrated nocturnal visits by dominant piscivorous fish species (rockfishes and conger eel) to the Seagrass Bed. We conclude that the nocturnal visits by piscivorous fishes increased the predation risk and trophic level in the fish nursery. The ecological functions of Seagrass Beds should be reevaluated accounting for day/night changes in food webs; these areas serve as nurseries for juvenile and small-sized fishes during the day and as foraging grounds for predators during the night.
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vulnerability of juvenile fish to piscivorous fish predators increases during nighttime in a Seagrass Bed in the central seto inland sea japan
2012Co-Authors: Hikari Kinoshita, Yasuhiro Kamimura, Kotaro Kirai, Kenichiro Mizuno, Yuji Iwamoto, Jun ShojiAbstract:To test the hypothesis that vulnerability to predation of small-sized fishes increases during nighttime, the fish species composition, a bundance, biomass and stomach contents of potential predators, and the mortality rate during tethering experiments were compared between daytime and nighttime at a Seagrass Bed in the central Seto Inland Sea, Japan. A total of 494 fishes belonging to 30 taxa were collected using a round seine on 28 and 30 August 2007. Abundance and biomass of potential fish predators (piscivorous fish >82.5 mm i n total length) were higher in nighttime than in daytime. Sebastes cheni juveniles and Rudaris ercodes were predated on by Sebastes inermis and Lateolabrax japonicus. Predation rate of juvenile S. cheni, a dominant species in the fish community, estimated from the ratio of the number of juveniles predated to that of population (sum of surviving and predated juveniles) during nighttime (1930–2100 h ) was 5.1%. Tethering experiments for 6 h at the Seagrass Bed indicated that the mortality rate of juvenile S. cheni in nighttime was significantly higher than that in daytime. It is plausible that Seagrass Beds contribute as foraging habitats for piscivorous fish during nighttime although they are important nurseries for a variety of fish species.
Pierre Chardy - One of the best experts on this subject based on the ideXlab platform.
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heterogeneity of macrozoobenthic assemblages within a zostera noltii Seagrass Bed diversity abundance biomass and structuring factors
Estuarine Coastal and Shelf Science, 2004Co-Authors: Hugues Blanchet, Xavier De Montaudouin, Aurelien Lucas, Pierre ChardyAbstract:Abstract The macrobenthic fauna community of a 70-km 2 Zostera noltii Seagrass Bed (Arcachon bay, France) was studied by sampling 49 stations systematically. A total of 126 taxa were identified. Cluster Analysis based on χ 2 distance showed that in this apparently homogeneous habitat, four distinct macrobenthic communities could be identified. Multiple Discriminant Analysis highlighted the major contribution of the overlying water mass as a forcing variable, and, to a lesser extent, of tidal level and Z. noltii 's below-ground parts. Seven stations did not constitute any conspicuous group, and were characterized by a low biomass of leaf ( −2 ), considered as the lowest value to constitute a Z. noltii community. Less than 24% of the Seagrass Bed was situated in more oceanic waters and at a quite low tidal level. In this relatively stable environment, the macrofauna community was characterized by a high species richness (mean = 39) and a moderate density and high biomass (12 638 individuals m −2 and 25 g AFDW m −2 , respectively). Annelids dominated, particularly the oligochaetes. When physical constraints increased (emersion or brackish water conditions), diversity decreased, abundance and biomass increased. The Seagrass Bed (55%) was flooded with highly fluctuating waters in term of temperature and salinity, here species richness was low (mean = 27) but abundance and biomass were high (24 384 individuals m −2 and 28 g AFDW m −2 , respectively), with a dominance of molluscs. The meadow (7%) was in external waters but at a higher tidal level (2.4 m vs 1.8 m above medium low tide level). This community was characterized by the particularly high density (41 826 individuals m −2 ) and dominance of oligochaetes (79% of total abundance). Species richness was high (mean = 37) here. A fourth community, extending over 12% of the meadow was dominated by the gastropod Hydrobia ulvae but could not be linked to a specific forcing variable. This study confirmed the almost complete replacement of the native clam Ruditapes decussatus by the Manila clam Ruditapes philippinarum since its introduction in the 1980s.
Charles R. Lovell - One of the best experts on this subject based on the ideXlab platform.
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Molecular diversity of diazotrophs in oligotrophic tropical Seagrass Bed communities
FEMS microbiology ecology, 2002Co-Authors: Christopher E. Bagwell, Jeannine R. La Rocque, Garriett W. Smith, Shawn W. Polson, Michael J. Friez, John W. Longshore, Charles R. LovellAbstract:Denaturing gradient gel electrophoresis (DGGE) was employed to resolve PCR-amplified nifH sequences from vegetated and unvegetated sediments from two oligotrophic Seagrass Bed sites on San Salvador Island, Bahamas, in order to assess diazotroph species composition. All DGGE profiles from these sites showed the same prominent bands. These bands were sequenced, yielding 67 different nifH sequences, which were used in phylogenetic reconstructions. Most sequences were from anaerobes, but some were affiliated with the alpha- and (gamma-+beta-) Proteobacteria. Several NifH sequences were nearly identical to those from Azospirillum brasilense and Vibrio diazotrophicus. These Seagrass Bed sediments support a diverse diazotroph assemblage that is, at least superficially, similar to that associated with an intertidal grass (Spartina alterniflora).
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molecular diversity of diazotrophs in oligotrophic tropical Seagrass Bed communities
FEMS Microbiology Ecology, 2002Co-Authors: Christopher E. Bagwell, Jeannine R. La Rocque, Garriett W. Smith, Shawn W. Polson, Michael J. Friez, John W. Longshore, Charles R. LovellAbstract:Denaturing gradient gel electrophoresis (DGGE) was employed to resolve PCR-amplified nifH sequences from vegetated and unvegetated sediments from two oligotrophic Seagrass Bed sites on San Salvador Island, Bahamas, in order to assess diazotroph species composition. All DGGE profiles from these sites showed the same prominent bands. These bands were sequenced, yielding 67 different nifH sequences, which were used in phylogenetic reconstructions. Most sequences were from anaerobes, but some were affiliated with the α- and (γ-+β-) Proteobacteria. Several NifH sequences were nearly identical to those from Azospirillum brasilense and Vibrio diazotrophicus. These Seagrass Bed sediments support a diverse diazotroph assemblage that is, at least superficially, similar to that associated with an intertidal grass (Spartina alterniflora).