Does water level affect benthic macro-invertebrates of a marginal lake in a tropical river-reservoir transition zone?

Benthic macro-invertebrates are important components of freshwater ecosystems which are involved in ecological processes such as energy transfer between detritus and consumers and organic matter recycling. The aim of this work was to investigate the variation in organism richness, diversity and density of benthic fauna during the annual cycle in Camargo Lake, a lake marginal to Paranapanema River, southeast Brazil. The correlation of environmental factors with community attributes of the macro-benthic fauna was assessed. Since Camargo Lake is connected to the river, we tested the hypothesis that water level variation is the main regulating factor of environmental variables and of the composition and abundance of benthic macro-invertebrates. The results indicated that lake depth varied with rainfall, being the highest at the end of the rising water period and the lowest at the beginning of this period. The sediment granulometry was more heterogeneous at the bottom of the lake by the end of the high water period. The benthic macro-invertebrate fauna was composed by 15 taxa. The Diptera order was represented by seven taxa and had greater richness in relation to other taxa. This group was responsible for 60% of the total abundance of organisms, followed by Ephemeroptera (22%) and Anellida (16%). Significant differences were observed over time in total richness and, in density of Narapa bonettoi, Chaoborus, Ablabesmyia gr. annulata, Chironomus gigas, Larsia fittkau, and Procladius sp. 2. Total taxa richness correlated negatively with water pH, transparency, conductivity, and bottom water oxygen. Higher positive correlations were found between the densities of some taxa and bottom water oxygen, conductivity and very fine sand, silt + clay of sediment, while negative correlations were recorded with organic matter, and fine, medium and coarse sand, bottom water temperature, mean temperature and rainfall. The significant temporal difference in water level was associated with changes in abiotic factors and macro-invertebrate community attributes.

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Coastal hypoxia and sediment biogeochemistry

Biogeosciences ◽

10.5194/bg-6-1273-2009 ◽

2009 ◽

Vol 6 (7) ◽

pp. 1273-1293 ◽

Cited By ~ 339

Author(s):

J. J. Middelburg ◽

L. A. Levin

Keyword(s):

Organic Matter ◽

Bottom Water ◽

Water Exchange ◽

Transport Processes ◽

Ecosystem Dynamics ◽

Ecosystem Functions ◽

Oxygen Levels ◽

Concise Review ◽

Water Oxygen ◽

Sediment Biogeochemistry

Abstract. The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal-induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification), there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis) with consequences for coastal ecosystem dynamics.

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Coastal hypoxia and sediment biogeochemistry

Biogeosciences Discussions ◽

10.5194/bgd-6-3655-2009 ◽

2009 ◽

Vol 6 (2) ◽

pp. 3655-3706 ◽

Cited By ~ 29

Author(s):

J. J. Middelburg ◽

L. A. Levin

Keyword(s):

Organic Matter ◽

Bottom Water ◽

Water Exchange ◽

Transport Processes ◽

Ecosystem Dynamics ◽

Ecosystem Functions ◽

Oxygen Levels ◽

Concise Review ◽

Water Oxygen ◽

Sediment Biogeochemistry

Abstract. The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification), there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis) with consequences for coastal ecosystem dynamics.

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Records of past mid-depth ventilation: Cretaceous ocean anoxic event 2 vs. Recent oxygen minimum zones

Biogeosciences ◽

10.5194/bg-12-1169-2015 ◽

2015 ◽

Vol 12 (4) ◽

pp. 1169-1189 ◽

Cited By ~ 10

Author(s):

J. Schönfeld ◽

W. Kuhnt ◽

Z. Erdem ◽

S. Flögel ◽

N. Glock ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Bottom Water ◽

Carbon Accumulation ◽

Marine Biota ◽

Accumulation Rates ◽

Oxygen Minimum Zones ◽

Oxygen Levels ◽

Water Oxygen ◽

Oxygen Minimum

Abstract. Present day oceans are well ventilated, with the exception of mid-depth oxygen minimum zones (OMZs) under high surface water productivity, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or anoxic. The Cretaceous ocean anoxic events (OAEs) were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossils preserved in the sedimentary record. Yet assessments of the intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life have been studied thoroughly. Their implications for constraining past bottom-water oxygenation are addressed in this review. We compared OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the north-west African shelf. Holocene laminated sediments are encountered at bottom-water oxygen levels of < 7 μmol kg−1 under the Peruvian upwelling and < 5 μmol kg−1 in California Borderland basins and the Pakistan Margin. Seasonal to decadal changes of sediment input are necessary to create laminae of different composition. However, bottom currents may shape similar textures that are difficult to discern from primary seasonal laminae. The millimetre-sized trace fossil Chondrites was commonly found in Cretaceous strata and Recent oxygen-depleted environments where its diameter increased with oxygen levels from 5 to 45 μmol kg−1. Chondrites has not been reported in Peruvian sediments but centimetre-sized crab burrows appeared around 10 μmol kg−1, which may indicate a minimum oxygen value for bioturbated Cretaceous strata. Organic carbon accumulation rates ranged from 0.7 and 2.8 g C cm−2 kyr−1 in laminated OAE 2 sections in Tarfaya Basin, Morocco, matching late Holocene accumulation rates of laminated Peruvian sediments under Recent oxygen levels below 5 μmol kg−1. Sediments deposited at > 10 μmol kg−1 showed an inverse exponential relationship of bottom-water oxygen levels and organic carbon accumulation depicting enhanced bioirrigation and decomposition of organic matter with increased oxygen supply. In the absence of seasonal laminations and under conditions of low burial diagenesis, this relationship may facilitate quantitative estimates of palaeo-oxygenation. Similarities and differences between Cretaceous OAEs and late Quaternary OMZs have to be further explored to improve our understanding of sedimentary systems under hypoxic conditions.

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The nitrogen isotope effect of benthic remineralization-nitrification-denitrification coupling in an estuarine environment

Biogeosciences ◽

10.5194/bg-9-1633-2012 ◽

2012 ◽

Vol 9 (5) ◽

pp. 1633-1646 ◽

Cited By ~ 40

Author(s):

M. Alkhatib ◽

M. F. Lehmann ◽

P. A. del Giorgio

Keyword(s):

Organic Matter ◽

Water Column ◽

Pore Water ◽

Bottom Water ◽

Isotope Fractionation ◽

N Loss ◽

N Transformations ◽

Lawrence Estuary ◽

Water Oxygen ◽

Oxygen Concentrations

Abstract. The nitrogen (N) stable isotopic composition of pore water nitrate and total dissolved N (TDN) was measured in sediments of the St. Lawrence Estuary and the Gulf of St. Lawrence. The study area is characterized by gradients in organic matter reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. N isotope effects on the water column associated with the benthic exchange of nitrate (εapp) and TDN (εsed) during benthic nitrification-denitrification coupling were investigated. The sediments were a major sink for nitrate and a source of reduced dissolved N (RDN = DON + NH4+). We observed that both the pore water nitrate and RDN pools were enriched in 15N relative to the water column, with increasing δ15N downcore in the sediments. As in other marine environments, the biological nitrate isotope fractionation of net fixed N loss was barely expressed at the scale of sediment-water exchange, with &varepsilon;app values <3‰. The strongest under-expression (i.e. lowest εapp) of the biological N isotope fractionation was observed at the most oxygenated sites with the least reactive organic matter, indicating that, through their control on the depth of the denitrification zone, bottom water oxygen concentrations and the organic matter reactivity can modulate εapp. For the first time, actual measurements of δ15N of pore water RDN were included in the calculations of εsed. We argue that large fractions of the sea-floor-derived DON are reactive and, hence, involved in the development of the δ15N of dissolved inorganic N (DIN) in the water column. In the St. Lawrence sediments, the combined benthic N transformations yield a flux of 15N-enriched RDN that can significantly elevate εsed above εapp. Calculated εsed values were within the range of 4.6 ± 2‰ and were related to organic matter reactivity and oxygen penetration depth in the sediments. &varepsilon;sed reflects the δ15N of the N2 lost from marine sediments and thus best describes the isotopic impact of fixed N loss from sediments on the oceanic fixed N pool. Our mean value for εsed is larger than assumed by earlier work, questioning current ideas with regards to the state of balance of the modern N budget.

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Systematics of past changes in ocean ventilation: a comparison of Cretaceous Ocean Anoxic Event 2 and Pleistocene to Holocene Oxygen Minimum Zones

Biogeosciences Discussions ◽

10.5194/bgd-11-13343-2014 ◽

2014 ◽

Vol 11 (9) ◽

pp. 13343-13387 ◽

Cited By ~ 2

Author(s):

J. Schönfeld ◽

W. Kuhnt ◽

Z. Erdem ◽

S. Flögel ◽

N. Glock ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Bottom Water ◽

Sediment Cores ◽

Carbon Accumulation ◽

Accumulation Rates ◽

Oxygen Minimum Zones ◽

Oxygen Levels ◽

Water Oxygen ◽

Oxygen Minimum

Abstract. Present day oceans are generally well ventilated except mid-depth oxygen minimum zones (OMZs) under high surface water productivity regimes, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or even anoxic. In particular the Cretaceous Ocean Anoxic Events (OAEs) were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossil assemblages preserved in the sedimentary record. Yet both, qualitative and quantitative assessments of intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life are well known. Their implications for constraining past bottom-water oxygenation are addressed in this review, with emphasis on comparing OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the Atlantic NW African shelf. Holocene laminated sediments were encountered at bottom-water oxygen levels of <7 μmol kg−1 under the Peruvian upwelling and <5 μmol kg−1 in California Borderland basins and the Pakistan Margin. Changes of sediment input on seasonal to decadal time scales are necessary to create laminae of different composition. However, bottom currents may shape similar textures that are difficult to discern from primary seasonal laminae in sediment cores. The millimetre-sized trace fossil Chondrites was commonly found in Cretaceous strata and Recent oxygen-depleted environments where its diameter increased with oxygen levels from 5 to 45 μmol kg−1. This ichnogenus has not been reported from Peruvian sediments but cm-sized crab burrows appeared around 10 μmol kg−1, which may indicate a minimum oxygen value for bioturbated Cretaceous strata. Organic carbon accumulation rates ranged from 0.7 and 2.8 g C cm−2 kyr−1 in laminated sections of OAE 2 in the Tarfaya Basin, Morocco, matching late Holocene accumulation rates of the majority of laminated Peruvian sediment cores under Recent oxygen levels below 5 μmol kg−1. Sediments deposited at >10 μmol kg−1 showed an inverse exponential relationship of bottom-water oxygen levels and organic carbon accumulation depicting enhanced bioirrigation and decomposition of organic matter with increased oxygen supply. In absence of seasonal laminations and under conditions of low burial diagenesis, this relationship may facilitate quantitative estimates of paleo-oxygenation under suboxic conditions. Similarities and differences between Cretaceous OAEs and late Quaternary OMZs have to be further explored to improve our understanding of sedimentary systems under hypoxic conditions.

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Multiproxy sedimentological and geochemical analyses across the Lower–Middle Pleistocene boundary: chemostratigraphy and paleoenvironment of the Chiba composite section, central Japan

Progress in Earth and Planetary Science ◽

10.1186/s40645-020-00393-5 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Kentaro Izumi ◽

Yuki Haneda ◽

Yusuke Suganuma ◽

Makoto Okada ◽

Yoshimi Kubota ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Bottom Water ◽

Middle Pleistocene ◽

Oxygen Level ◽

Terrigenous Material ◽

Central Japan ◽

Water Oxygen ◽

Composite Section ◽

Geochemical Analyses

AbstractThe Chiba composite section (CbCS) in the Kokumoto Formation, Kazusa Group, central Japan is a thick and continuous marine succession that straddles the Lower–Middle Pleistocene boundary and the well-recognized Matuyama–Brunhes paleomagnetic polarity boundary. Although recent studies extensively investigated the CbCS, its chemostratigraphy, particularly around the Lower–Middle Pleistocene boundary, is poorly understood. Therefore, in this study, we performed multiproxy sedimentological and geochemical analyses of the CbCS, including the Chiba section, which is the Global Boundary Stratotype Section and Point for defining the base of the Middle Pleistocene Subseries. The aim of these analyses is to establish the high-resolution chemostratigraphy and to reconstruct the paleoenvironments of its sedimentary basin in detail. We used the K/Ti ratio as a broad proxy for the clastic material grain size of the sediments. Although the K/Ti ratio generally varies throughout the studied interval, the K/Ti ratio especially during Marine Isotope Stage (MIS) 19a shows a variation pattern like those of the foraminiferal oxygen isotope (δ18O) records. The records of the C/N ratio of bulk samples and carbon isotope ratio of the organic carbon (δ13Corg) suggest that the organic matter in the CbCS sediments during MIS 19c mostly originated from marine plankton, whereas the organic matter during MIS 18 and 19a was characterized by a mixture of marine plankton and terrestrial plants. These records are clearly indicative of changes in mixing ratio of marine vs. terrestrial organic matter in association with glacial–interglacial cycles from the late MIS 20 to the early MIS 18. In addition, we calculated the mass accumulation rates (MARs) of organic carbon, biogenic carbonate, and terrigenous material for quantitative interpretations on the paleoenvironmental changes. MAR calculations revealed that the contribution of marine organic carbon relative to terrestrial organic carbon increased during MIS 19c, and that the contribution of the terrigenous material relative to biogenic carbonate decreased during MIS 19c. Furthermore, we observed relatively large variations in the total organic carbon and total nitrogen contents during MIS 19a. These variations were probably caused by the relative decrease in bottom-water oxygen level, which is also supported by our trace-fossil data, although it is not certain whether the increase in organic-carbon flux at ~ 760 ka was due to the synchronous increase in biogenic productivity in surface water. Such a relative decrease in bottom-water oxygen level was partly due to the increased ocean stratification because of the northward displacement of the Kuroshio Extension Front.

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The nitrogen isotope effect of benthic remineralization-nitrification-denitrification coupling in an estuarine environment

Biogeosciences Discussions ◽

10.5194/bgd-8-11689-2011 ◽

2011 ◽

Vol 8 (6) ◽

pp. 11689-11723

Author(s):

M. Alkhatib ◽

M. F. Lehmann ◽

P. A. del Giorgio

Keyword(s):

Organic Matter ◽

Water Column ◽

Pore Water ◽

Bottom Water ◽

Isotope Fractionation ◽

N Budget ◽

N Transformations ◽

Lawrence Estuary ◽

Water Oxygen ◽

Oxygen Concentrations

Abstract. The nitrogen (N) stable isotopic composition of pore water nitrate and total dissolved N (TDN) was measured in sediments of the St. Lawrence Estuary and the Gulf of St. Lawrence. The study area is characterized by gradients in organic matter reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. Benthic N isotope exchange, as well as the nitrate and TDN isotope effects of benthic nitrification-denitrification coupling on the water column, &varepsilon;app and &varepsilon;sed, respectively, were investigated. The sediments were a major sink for nitrate and a source of reduced dissolved N (RDN = DON + NH4+). We observed that both the pore water nitrate and RDN pools were enriched in 15N relative to the water column, with increasing δ15N downcore in the sediments. As in other marine environments, the biological nitrate isotope fractionation of net nitrate elimination was barely expressed at the scale of sediment-water-exchange, with &varepsilon;app values <3‰. The strongest under-expression of the biological N isotope fractionation was observed at the most oxygenated sites with the least reactive organic matter, indicating that, through their control on the depth of the denitrification zone, bottom water oxygen concentrations and the organic matter reactivity can modulate &varepsilon;app. For the first time, actual measurements of δ15N of pore water RDN were included in the calculations of &varepsilon;sed. We argue that large fractions of the sea-floor-derived DON are reactive and, hence, involved in the development of the δ15N of dissolved inorganic N (DIN) in the water column. In the St. Lawrence sediments, the combined benthic N transformations yield a flux of 15N-enriched RDN that can significantly enhance &varepsilon;sed. Calculated &varepsilon;sed values were within the range of 4.6 ± 2‰, and were related to organic matter reactivity and oxygen penetration depth in the sediments. &varepsilon;sed reflects the δ15N of the N2 lost from marine sediments and thus best describes the isotopic impact of N elimination on the oceanic fixed N pool. Our mean value for &varepsilon;sed is larger than assumed by earlier work, questioning current ideas with regards to the state of balance of the modern N budget.

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Benthic fluxes of dissolved organic nitrogen in the lower St. Lawrence estuary and implications for selective organic matter degradation

Biogeosciences ◽

10.5194/bg-10-7609-2013 ◽

2013 ◽

Vol 10 (11) ◽

pp. 7609-7622 ◽

Cited By ~ 13

Author(s):

M. Alkhatib ◽

P. A. del Giorgio ◽

Y. Gelinas ◽

M. F. Lehmann

Keyword(s):

Organic Matter ◽

Dissolved Organic Nitrogen ◽

Organic Nitrogen ◽

Bottom Water ◽

Estuarine Sediments ◽

Internal Source ◽

Lawrence Estuary ◽

Element Partitioning ◽

Sediment Porewaters ◽

St Lawrence Estuary

Abstract. The distribution of dissolved organic nitrogen (DON) and carbon (DOC) in sediment porewaters was determined at nine locations along the St. Lawrence estuary and in the gulf of St. Lawrence. In a previous manuscript (Alkhatib et al., 2012a), we have shown that this study area is characterized by gradients in the sedimentary particulate organic matter (POM) reactivity, bottom water oxygen concentrations, and benthic respiration rates. Based on the porewater profiles, we estimated the benthic diffusive fluxes of DON and DOC in the same area. Our results show that DON fluxed out of the sediments at significant rates (110 to 430 μmol m−2 d−1). DON fluxes were positively correlated with sedimentary POM reactivity and varied inversely with sediment oxygen exposure time (OET), suggesting direct links between POM quality, aerobic remineralization and the release of DON to the water column. DON fluxes were on the order of 30 to 64% of the total benthic inorganic fixed N loss due to denitrification, and often exceeded the diffusive nitrate fluxes into the sediments. Hence they represented a large fraction of the total benthic N exchange, a result that is particularly important in light of the fact that DON fluxes are usually not accounted for in estuarine and coastal zone nutrient budgets. In contrast to DON, DOC fluxes out of the sediments did not show any significant spatial variation along the Laurentian Channel (LC) between the estuary and the gulf (2100 ± 100 μmol m−2 d−1). The molar C / N ratio of dissolved organic matter (DOM) in porewater and the overlying bottom water varied significantly along the transect, with lowest C / N in the lower estuary (5–6) and highest C / N (> 10) in the gulf. Large differences between the C / N ratios of porewater DOM and POM are mainly attributed to a combination of selective POM hydrolysis and elemental fractionation during subsequent DOM mineralization, but selective adsorption of DOM to mineral phases could not be excluded as a potential C / N fractionating process. The extent of this C- versus N- element partitioning seems to be linked to POM reactivity and redox conditions in the sediment porewaters. Our results thus highlight the variable effects selective organic matter (OM) preservation can have on bulk sedimentary C / N ratios, decoupling the primary source C / N signatures from those in sedimentary paleoenvironmental archives. Our study further underscores that the role of estuarine sediments as efficient sinks of bioavailable nitrogen is strongly influenced by the release of DON during early diagenetic reactions, and that DON fluxes from continental margin sediments represent an important internal source of N to the ocean.

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Linking Genes to Traits in Fungi

Microbial Ecology ◽

10.1007/s00248-021-01687-x ◽

2021 ◽

Author(s):

A. L. Romero-Olivares ◽

E. W. Morrison ◽

A. Pringle ◽

S. D. Frey

Keyword(s):

Organic Matter ◽

Nitrogen Uptake ◽

Brown Rot ◽

Terrestrial Ecosystems ◽

Organic Matter Decomposition ◽

Gene Frequencies ◽

Ecological Processes ◽

Linked Gene ◽

Carbon Cycles ◽

Brown Rot Fungi

AbstractFungi are mediators of the nitrogen and carbon cycles in terrestrial ecosystems. Examining how nitrogen uptake and organic matter decomposition potential differs in fungi can provide insight into the underlying mechanisms driving fungal ecological processes and ecosystem functioning. In this study, we assessed the frequency of genes encoding for specific enzymes that facilitate nitrogen uptake and organic matter decomposition in 879 fungal genomes with fungal taxa grouped into trait-based categories. Our linked gene-trait data approach revealed that gene frequencies vary across and within trait-based groups and that trait-based categories differ in trait space. We present two examples of how this linked gene-trait approach can be used to address ecological questions. First, we show that this type of approach can help us better understand, and potentially predict, how fungi will respond to environmental stress. Specifically, we found that trait-based categories with high nitrogen uptake gene frequency increased in relative abundance when exposed to high soil nitrogen enrichment. Second, by comparing frequencies of nitrogen uptake and organic matter decomposition genes, we found that most ectomycorrhizal fungi in our dataset have similar gene frequencies to brown rot fungi. This demonstrates that gene-trait data approaches can shed light on potential evolutionary trajectories of life history traits in fungi. We present a framework for exploring nitrogen uptake and organic matter decomposition gene frequencies in fungal trait-based groups and provide two concise examples on how to use our framework to address ecological questions from a mechanistic perspective.

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Temporal partitioning of reproductive activity in a neotropical anuran community

Journal of Tropical Ecology ◽

10.1017/s0266467403001172 ◽

2004 ◽

Vol 20 (3) ◽

pp. 271-280 ◽

Cited By ~ 75

Author(s):

Brigitte Gottsberger ◽

Edith Gruber

Keyword(s):

Water Level ◽

Rainy Season ◽

Abiotic Factors ◽

Reproductive Mode ◽

Reproductive Activity ◽

Active Species ◽

South American ◽

Wet Season ◽

Breeding Sites ◽

Calling Activity

The phenology of calling activity and reproduction of a neotropical anuran community in French Guiana was studied during one rainy season. We investigated the correlation between calling activity, rainfall, temperature and water level in two ponds and recorded the occurrence of tadpoles of pond-breeding species. The study site contained 31 calling frog species, which were divided into groups according to reproductive mode. Increased rainfall was associated with increased reproductive activity in all groups, but temporal patterns in calling activity varied significantly between groups. Species with aquatic oviposition exhibited sporadic acoustic activity, aggregating into explosive breeding events following heavy rainfall. Species laying eggs in foam nests had the peak of calling activity at the start of the rainy season. Taxa with embryonic development on vegetation called mainly from middle to late wet season, being the only group which showed a significant correlation of calling with increasing water level. Dendrobatids with terrestrial oviposition and subsequent parental tadpole transportation were continuously active. Species with direct development or with non-feeding larvae were mainly active at the beginning of the rainy season. It is concluded that phenologies of calling activity in South American tropical anuran species are strongly influenced by abiotic factors like rainfall and availability of breeding sites. The temporal limitation of the rainy season forces species to adjust calling and reproductive activity according to their reproductive modes.

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