Erik Kristensen | University of Southern Denmark (original) (raw)

Papers by Erik Kristensen

Journal of Experimental Marine Biology and Ecology, 2011

Estimation of Taylor's power law for species abundance data may be performed by linear regression... more Estimation of Taylor's power law for species abundance data may be performed by linear regression of the log empirical variances on the log means, but this method suffers from a problem of bias for sparse data. We show that the bias may be reduced by using a biascorrected Pearson estimating function. Furthermore, we investigate a more general regression model allowing for site-specific covariates. This method may be efficiently implemented using a Newton scoring algorithm, with standard errors calculated from the inverse Godambe information matrix. The method is applied to a set of biomass data for benthic macrofauna from two Danish estuaries.

Earth-Science Reviews

ABSTRACT Mangroves, saltmarsh plants and seagrasses grow in coastal areas near the land-ocean int... more ABSTRACT Mangroves, saltmarsh plants and seagrasses grow in coastal areas near the land-ocean interface. Marine scientists normally identify the substratum in which these plants grow as sediments. For half a century, sediments supporting emergent vegetation have been described by pedologists and some ecologists as soils. However, more recently, some pedologists began to suggest that subtidal marine substrata should be considered to be “subaqueous soils.” This followed a change in the definition of soil in the 2nd (1999) edition of Soil Taxonomy by the US Department of Agriculture. These developments have caused concerns among many coastal marine scientists, and have led to the emergence of serious and important questions which we address in this paper. We conclude that the use of “sediment” and “soil” to describe the substrata in coastal environments vegetated by mangrove forests, saltmarshes and seagrass beds are not mutually exclusive. Coastal marine substrata will still be denoted sediments by most marine scientists. Pedologists should recognize and affirm the appropriateness of this historical convention, while they at the same time for specific purposes can use the term “soil” when justifiable according to the definition. Furthermore, research methodology must be appropriate to the environments under study and recognize the uniqueness of these water saturated and largely anoxic environments. This is critical to avoid flawed and incomparable results and to facilitate better communication among scientists working in the coastal zone. A mutual awareness and appreciation among involved communities will help to avoid confusion and improve the understanding among the marine and soil researchers studying these systems. We hope that these ideas can be adopted by the marine and terrestrial scientific communities and look forward to further cooperation through a continued positive dialogue.

Coastal and Estuarine Studies

Construction and maintenance of burrows by macrofauna have large implications for the microbiolog... more Construction and maintenance of burrows by macrofauna have large implications for the microbiology and biogeochemistry of marine sediments. Although a wealth of new information has become available during the last few decades, there are still significant gaps in our knowledge. In this chapter, we review the current understanding of how the structure and function of irrigated burrows affect the composition of microbial communities and associated biogeochemical processes. Although a general relationship is observed between burrow depth and diameter (inhabitant width), it is difficult to classify burrow architecture in relation to the function and trophic mode of macrofaunal inhabitants. Trophic mode (suspension-feeding versus deposit-feeding) appears to control burrow wall structure and irrigation rate and thus the exchange of solutes between sediment porewaters and the overlying water. The associated translocation of electron acceptors into and inhibitory metabolites out of the sediment in turn affects diagenetic reactions. It is well established that irrigated burrows enhance total microbial metabolism by stimulating oxic (e.g. respiration) and suboxic (e.g. nitrification-denitrification and iron reduction) reactions in the surrounding sediment. In contrast, the impacts of burrowgenerated changes to diffusion scales on anoxic processes like sulfate reduction are less clear. Sediments surrounding burrow structures likely support unique microbial communities that differ from those in surficial sediments due to large differences in environmental conditions. Biogeochemical evidence clearly indicates that the activity and abundance of microorganisms are elevated around burrows. However, the mechanisms controlling microbially mediated geochemical reactions in the burrow zone remain understudied, and very little information is available to assess the impacts of burrow environments on the community structure or diversity of microorganisms. Therefore, we cannot yet generalize about direct relationships between burrows, irrigation and the distribution of microorganisms. However, much progress is already being made through the use of new and exciting experimental tools, such as microsensors and cultivation-independent molecular techniques.

Environmental Pollution, Jan 31, 2010

Terebralia palustris high ecosystem engineering potential in constructed mangrove wetlands.

Estuar Coast Shelf Sci, 2005

Carbon and nitrogen budgets for the leaf-eating crab, Neoepisesarma versicolor, were established ... more Carbon and nitrogen budgets for the leaf-eating crab, Neoepisesarma versicolor, were established for individuals living on pure leaf diets. Crabs were fed fresh (green), senescent (yellow) and partly degraded (brown) leaves of the mangrove tree Rhizophora apiculata. Ingestion, ...

Continental Shelf Research, 1999

Carbon and nitrogen mineralization were determined in sediments from about 100 to 1000 m depth on... more Carbon and nitrogen mineralization were determined in sediments from about 100 to 1000 m depth on the continental shelf and slope o! the Paci"c coast of Mexico and Washington State. Vertical down core pro"les of carbon mineralization were measured both as sulfate reduction using short-term S incubations and as net TCO production using long-term anaerobic incubations (&jar' technique). Nitrogen mineralization was measured as net NH> production using only the latter technique. The down core attenuation of jar rates was described adequately by a double exponential decay model. By subtraction of S rates from jar rates in the upper 3 cm of the sediment, oxic plus suboxic respiration were roughly estimated to account for at least 5}28% (Mexico) and 10}19% (Washington) of the 0}30 cm integrated carbon mineralization. The agreement between measured porewater pro"les of TCO and NH> and those estimated by diagenetic modelling using rates obtained from jar incubations in the oxygen de"cient zone o! Mexico indicated no infaunal irrigation. At all other stations the benthic fauna appeared responsible for considerably lower measured porewater concentrations than predicted by a simple di!usion-based diagenetic model. Total carbon mineralization in sediments o! Mexico was reduced 40% with water depth from 100}200 m to 1000 m, while the reduction in the same depth interval o! Washington was about 80%. Water depth attenuation of total sediment nitrogen mineralization at the two locations, on the other hand, was almost similar with a reduction of 70}80%. The overall molar C : N ratio of mineralization products was generally higher o! Washington than in the oxygen de"cient zone o! Mexico. It is suggested that the di!erence in sediment mineralization patterns are associated with changes in water column processes related to the di!erent strength of the oxygen minimum at the two locations.

Biogeochemistry, Jul 4, 2009

Phuket Marine Biological Center Research Bulletin, 1995

Limnology and Oceanography, 2006

The influence of mangrove saplings (Avicennia marina) and fiddler crabs (Uca vocans) on carbon, i... more The influence of mangrove saplings (Avicennia marina) and fiddler crabs (Uca vocans) on carbon, iron, and sulfur biogeochemistry in mangrove sediment was studied using outdoor mesocosms with and without plants (21 m 22 ) and crabs (68 m 22

Biogeochemistry, Feb 28, 1990

Journal of Experimental Marine Biology and Ecology, Dec 31, 1998

The combined impact of the burrow-dwelling polychaete, Nereis diversicolor, and organic enrichmen... more The combined impact of the burrow-dwelling polychaete, Nereis diversicolor, and organic enrichment with macroalgal detritus, Chaetomorpha linum, on sediment metabolism (CO 2 1 2 production) and nutrient (NH and NO ) dynamics was assessed in laboratory microcosms over 4 3 enrichment had a minor influence on this particular process.

Aktuel Naturvidenskab, 2014

Journal of Marine Research, Apr 30, 1991

The burrows of macroinfauna are significant sites of sediment -water nitrogen exchange and associ... more The burrows of macroinfauna are significant sites of sediment -water nitrogen exchange and associated microbial activity. In this study, the exchange of dissolved inorganic nitrogen (DIN) and nitrogen cycle reaction rates were quantified in individual burrows of the estuarine polychaete Nereis virens. Burrow ventilation rate and DIN (NH/, N0 2 -, N0 3 -and N20) exchange were determined at 22°C in individual, inhabited burrows with and without the presence of~H2 (an NH/ oxidation, N 2 0 reduction block). Ventilation cycles were unaffected by~H2' but worm metabolism (02 uptake) and excretion of NH/ were enhanced by -100% and -50%, respectively. Time-specific DIN exchange patterns were quantitatively modeled by relating burrow water concentration changes, excretion, and ventilation rates. The highest rates were at the start of ventilation periods and decreased or increased (depending on the solute) exponentially to a steady state level. The presence of~H2 increased NH4 + release from burrows and changed the N0 2 -flux from a high release (-300 nmol h-1 ) to an uptake (--30 nmol hOI). Nitrate uptake was independent of~H2' presumably because overlying water N0 3 -concentration was high (-100 ILM). Indirect estimates of nitrification corresponded to the burrow release of N0 2 -without~H2' Approximately half of the N0 2 -+ N0 3uptake in burrows was due to denitrification. In microcosms with and without N. virens (875 m-2 ), denitrification was stimulated 3-fold by N virens and the ratio denitrification/ nitrification increased from 0.61 to 1.11. The changes in DIN flux and denitrification caused by N virens corresponded well to the rates extrapolated from individual burrows to the appropriate worm density of 875 m-2 . At the abundance used, N. virens burrows were responsible for 37% and 66% ofthe total sediment nitrification and denitrification, respectively.

The most recent climate change scenarios for Denmark based on IPCC (2013) predict an increase of ... more The most recent climate change scenarios for Denmark based on IPCC (2013) predict an increase of 1.2-3.7°C in average annual temperature, 1.6-6.9% increase in precipitation and 0.34-0.61 m sea level rise for the period 2081-2100 compared with the reference period 1986 -2005 (Olesen et al. 2014. Many low-lying coastal areas in Denmark will be threatened by sea level rise. Coastal lagoons created by coastal realignment can act as buffer-zones against such threats and will probably also decrease the net-emission of CO 2 to the atmosphere. will monitor the chemical, physical and biological successions within the lagoon over the next 8 years, starting in May 2014. The project is unique because it is the first time an agricultural area of this size is flooded by seawater and monitored closely. The research will provide knowledge on changes ecological and biogeochemical functioning through time. An important aspect in this context is to examine the carbon balance in the new coastal lagoon in other words, to test if the emission of CO 2 to the atmosphere will increase or decrease compared to the situation before flooding.

Scientific Reports, 2015

2− reduction was detected in any season. Redox profiles suggested that conditions were less reduc... more 2− reduction was detected in any season. Redox profiles suggested that conditions were less reduced in February 2014 than in September 2012, probably associated with low reactivity of the organic matter, higher rates of aerobic respiration and bioirrigation by the higher density of small-macrofauna. Bioturbation by small macrofauna may maintain the sediment oxidized in summer, while large-sized species stimulate the reoxidation of reduced compounds throughout the year. Therefore, bioturbation seems to have an important role modulating the pathways of carbon mineralization in the area.

Journal of Experimental Marine Biology and Ecology, 2011

Estimation of Taylor's power law for species abundance data may be performed by linear regression... more Estimation of Taylor's power law for species abundance data may be performed by linear regression of the log empirical variances on the log means, but this method suffers from a problem of bias for sparse data. We show that the bias may be reduced by using a biascorrected Pearson estimating function. Furthermore, we investigate a more general regression model allowing for site-specific covariates. This method may be efficiently implemented using a Newton scoring algorithm, with standard errors calculated from the inverse Godambe information matrix. The method is applied to a set of biomass data for benthic macrofauna from two Danish estuaries.

Earth-Science Reviews

ABSTRACT Mangroves, saltmarsh plants and seagrasses grow in coastal areas near the land-ocean int... more ABSTRACT Mangroves, saltmarsh plants and seagrasses grow in coastal areas near the land-ocean interface. Marine scientists normally identify the substratum in which these plants grow as sediments. For half a century, sediments supporting emergent vegetation have been described by pedologists and some ecologists as soils. However, more recently, some pedologists began to suggest that subtidal marine substrata should be considered to be “subaqueous soils.” This followed a change in the definition of soil in the 2nd (1999) edition of Soil Taxonomy by the US Department of Agriculture. These developments have caused concerns among many coastal marine scientists, and have led to the emergence of serious and important questions which we address in this paper. We conclude that the use of “sediment” and “soil” to describe the substrata in coastal environments vegetated by mangrove forests, saltmarshes and seagrass beds are not mutually exclusive. Coastal marine substrata will still be denoted sediments by most marine scientists. Pedologists should recognize and affirm the appropriateness of this historical convention, while they at the same time for specific purposes can use the term “soil” when justifiable according to the definition. Furthermore, research methodology must be appropriate to the environments under study and recognize the uniqueness of these water saturated and largely anoxic environments. This is critical to avoid flawed and incomparable results and to facilitate better communication among scientists working in the coastal zone. A mutual awareness and appreciation among involved communities will help to avoid confusion and improve the understanding among the marine and soil researchers studying these systems. We hope that these ideas can be adopted by the marine and terrestrial scientific communities and look forward to further cooperation through a continued positive dialogue.

Coastal and Estuarine Studies

Construction and maintenance of burrows by macrofauna have large implications for the microbiolog... more Construction and maintenance of burrows by macrofauna have large implications for the microbiology and biogeochemistry of marine sediments. Although a wealth of new information has become available during the last few decades, there are still significant gaps in our knowledge. In this chapter, we review the current understanding of how the structure and function of irrigated burrows affect the composition of microbial communities and associated biogeochemical processes. Although a general relationship is observed between burrow depth and diameter (inhabitant width), it is difficult to classify burrow architecture in relation to the function and trophic mode of macrofaunal inhabitants. Trophic mode (suspension-feeding versus deposit-feeding) appears to control burrow wall structure and irrigation rate and thus the exchange of solutes between sediment porewaters and the overlying water. The associated translocation of electron acceptors into and inhibitory metabolites out of the sediment in turn affects diagenetic reactions. It is well established that irrigated burrows enhance total microbial metabolism by stimulating oxic (e.g. respiration) and suboxic (e.g. nitrification-denitrification and iron reduction) reactions in the surrounding sediment. In contrast, the impacts of burrowgenerated changes to diffusion scales on anoxic processes like sulfate reduction are less clear. Sediments surrounding burrow structures likely support unique microbial communities that differ from those in surficial sediments due to large differences in environmental conditions. Biogeochemical evidence clearly indicates that the activity and abundance of microorganisms are elevated around burrows. However, the mechanisms controlling microbially mediated geochemical reactions in the burrow zone remain understudied, and very little information is available to assess the impacts of burrow environments on the community structure or diversity of microorganisms. Therefore, we cannot yet generalize about direct relationships between burrows, irrigation and the distribution of microorganisms. However, much progress is already being made through the use of new and exciting experimental tools, such as microsensors and cultivation-independent molecular techniques.

Environmental Pollution, Jan 31, 2010

Terebralia palustris high ecosystem engineering potential in constructed mangrove wetlands.

Estuar Coast Shelf Sci, 2005

Carbon and nitrogen budgets for the leaf-eating crab, Neoepisesarma versicolor, were established ... more Carbon and nitrogen budgets for the leaf-eating crab, Neoepisesarma versicolor, were established for individuals living on pure leaf diets. Crabs were fed fresh (green), senescent (yellow) and partly degraded (brown) leaves of the mangrove tree Rhizophora apiculata. Ingestion, ...

Continental Shelf Research, 1999

Carbon and nitrogen mineralization were determined in sediments from about 100 to 1000 m depth on... more Carbon and nitrogen mineralization were determined in sediments from about 100 to 1000 m depth on the continental shelf and slope o! the Paci"c coast of Mexico and Washington State. Vertical down core pro"les of carbon mineralization were measured both as sulfate reduction using short-term S incubations and as net TCO production using long-term anaerobic incubations (&jar' technique). Nitrogen mineralization was measured as net NH> production using only the latter technique. The down core attenuation of jar rates was described adequately by a double exponential decay model. By subtraction of S rates from jar rates in the upper 3 cm of the sediment, oxic plus suboxic respiration were roughly estimated to account for at least 5}28% (Mexico) and 10}19% (Washington) of the 0}30 cm integrated carbon mineralization. The agreement between measured porewater pro"les of TCO and NH> and those estimated by diagenetic modelling using rates obtained from jar incubations in the oxygen de"cient zone o! Mexico indicated no infaunal irrigation. At all other stations the benthic fauna appeared responsible for considerably lower measured porewater concentrations than predicted by a simple di!usion-based diagenetic model. Total carbon mineralization in sediments o! Mexico was reduced 40% with water depth from 100}200 m to 1000 m, while the reduction in the same depth interval o! Washington was about 80%. Water depth attenuation of total sediment nitrogen mineralization at the two locations, on the other hand, was almost similar with a reduction of 70}80%. The overall molar C : N ratio of mineralization products was generally higher o! Washington than in the oxygen de"cient zone o! Mexico. It is suggested that the di!erence in sediment mineralization patterns are associated with changes in water column processes related to the di!erent strength of the oxygen minimum at the two locations.

Biogeochemistry, Jul 4, 2009

Phuket Marine Biological Center Research Bulletin, 1995

Limnology and Oceanography, 2006

The influence of mangrove saplings (Avicennia marina) and fiddler crabs (Uca vocans) on carbon, i... more The influence of mangrove saplings (Avicennia marina) and fiddler crabs (Uca vocans) on carbon, iron, and sulfur biogeochemistry in mangrove sediment was studied using outdoor mesocosms with and without plants (21 m 22 ) and crabs (68 m 22

Biogeochemistry, Feb 28, 1990

Journal of Experimental Marine Biology and Ecology, Dec 31, 1998

The combined impact of the burrow-dwelling polychaete, Nereis diversicolor, and organic enrichmen... more The combined impact of the burrow-dwelling polychaete, Nereis diversicolor, and organic enrichment with macroalgal detritus, Chaetomorpha linum, on sediment metabolism (CO 2 1 2 production) and nutrient (NH and NO ) dynamics was assessed in laboratory microcosms over 4 3 enrichment had a minor influence on this particular process.

Aktuel Naturvidenskab, 2014

Journal of Marine Research, Apr 30, 1991

The burrows of macroinfauna are significant sites of sediment -water nitrogen exchange and associ... more The burrows of macroinfauna are significant sites of sediment -water nitrogen exchange and associated microbial activity. In this study, the exchange of dissolved inorganic nitrogen (DIN) and nitrogen cycle reaction rates were quantified in individual burrows of the estuarine polychaete Nereis virens. Burrow ventilation rate and DIN (NH/, N0 2 -, N0 3 -and N20) exchange were determined at 22°C in individual, inhabited burrows with and without the presence of~H2 (an NH/ oxidation, N 2 0 reduction block). Ventilation cycles were unaffected by~H2' but worm metabolism (02 uptake) and excretion of NH/ were enhanced by -100% and -50%, respectively. Time-specific DIN exchange patterns were quantitatively modeled by relating burrow water concentration changes, excretion, and ventilation rates. The highest rates were at the start of ventilation periods and decreased or increased (depending on the solute) exponentially to a steady state level. The presence of~H2 increased NH4 + release from burrows and changed the N0 2 -flux from a high release (-300 nmol h-1 ) to an uptake (--30 nmol hOI). Nitrate uptake was independent of~H2' presumably because overlying water N0 3 -concentration was high (-100 ILM). Indirect estimates of nitrification corresponded to the burrow release of N0 2 -without~H2' Approximately half of the N0 2 -+ N0 3uptake in burrows was due to denitrification. In microcosms with and without N. virens (875 m-2 ), denitrification was stimulated 3-fold by N virens and the ratio denitrification/ nitrification increased from 0.61 to 1.11. The changes in DIN flux and denitrification caused by N virens corresponded well to the rates extrapolated from individual burrows to the appropriate worm density of 875 m-2 . At the abundance used, N. virens burrows were responsible for 37% and 66% ofthe total sediment nitrification and denitrification, respectively.

The most recent climate change scenarios for Denmark based on IPCC (2013) predict an increase of ... more The most recent climate change scenarios for Denmark based on IPCC (2013) predict an increase of 1.2-3.7°C in average annual temperature, 1.6-6.9% increase in precipitation and 0.34-0.61 m sea level rise for the period 2081-2100 compared with the reference period 1986 -2005 (Olesen et al. 2014. Many low-lying coastal areas in Denmark will be threatened by sea level rise. Coastal lagoons created by coastal realignment can act as buffer-zones against such threats and will probably also decrease the net-emission of CO 2 to the atmosphere. will monitor the chemical, physical and biological successions within the lagoon over the next 8 years, starting in May 2014. The project is unique because it is the first time an agricultural area of this size is flooded by seawater and monitored closely. The research will provide knowledge on changes ecological and biogeochemical functioning through time. An important aspect in this context is to examine the carbon balance in the new coastal lagoon in other words, to test if the emission of CO 2 to the atmosphere will increase or decrease compared to the situation before flooding.

Scientific Reports, 2015

2− reduction was detected in any season. Redox profiles suggested that conditions were less reduc... more 2− reduction was detected in any season. Redox profiles suggested that conditions were less reduced in February 2014 than in September 2012, probably associated with low reactivity of the organic matter, higher rates of aerobic respiration and bioirrigation by the higher density of small-macrofauna. Bioturbation by small macrofauna may maintain the sediment oxidized in summer, while large-sized species stimulate the reoxidation of reduced compounds throughout the year. Therefore, bioturbation seems to have an important role modulating the pathways of carbon mineralization in the area.