Kam W Tang

Swansea University | SWAN · Department of Biosciences

Aquaculture ponds serve as focal points for carbon cycling and act as anthropogenic contributors to the emission of carbon dioxide (CO2). To understand the seasonal CO2 dynamics within the ponds, we measured the CO2 concentrations in sediment porewater and the water column in aquaculture ponds in the Shanyutan Wetland in China. Subsequently, the se...

Aquaculture ponds are potential hotspots for carbon cycling and emission of greenhouse gases (GHGs) like CO2 and CH4, but they are often poorly assessed in the global GHG budget. This study determined the temporal variations of CO2 and CH4 concentrations and diffusive fluxes and their environmental drivers in coastal aquaculture ponds in southeaste...

Soil organic nitrogen (SON) turnover regulates soil nitrogen (N) storage and availability. The coastal mudflats (MFs) in China have undergone drastic transformation due to invasive Spartina alterniflora (SAs) and subsequent reclamation of Spartina marshes to create aquaculture ponds (APs), but the impact on the amounts and compositions of soil nitr...

The use of beneficial microbes, i.e., probiotics, to reduce pathogens and promote the performance of the target species is an important management strategy in mariculture. This study aimed to investigate the potential of four microbes, Debaryomyces hansenii, Ruegeria mobilis, Lactobacillus plantarum, and Bacillus subtilis, to suppress Vibrio and in...

Complete ammonia oxidizers (comammox Nitrospira) are ubiquitous in coastal wetland sediments and play an important role in nitrification. Our study examined the impact of habitat modifications on comammox Nitrospira communities in coastal wetland sediments across tropical and subtropical regions of southeastern China. Samples were collected from 21...

The extensive conversion of carbon-rich coastal wetland to aquaculture ponds in the Asian Pacific region has caused significant changes to the sediment properties and carbon cycling. Using field sampling and incubation experiments, the sediment anaerobic CO2 production and CO2 emission flux were compared between a brackish marsh and the nearby cons...

Wetland sediment is an important nitrogen pool and a source of the greenhouse gas nitrous oxide (N2O). Modification of coastal wetland landscape due to plant invasion and aquaculture activities may drastically change this N pool and the related dynamics of N2O. This study measured the sediment properties, N2O production and relevant functional gene...

Symsagittifera roscoffensis is an intertidal Acoel flatworm that forms a symbiotic relationship with the alga Tetraselmis convolutae. Members of the genus Tetraselmis are known to have a high nutritional value and have been widely used to enrich intermediate prey for fish within the aquaculture industry; therefore, S. roscoffensis could be a good c...

Coastal wetlands are important to the global carbon (C) budget and climate regulation. Plant invasion and aquaculture reclamation have drastically transformed China’s coastal wetlands, but knowledge of the effects on sediment carbon remains limited. We sampled top layer sediments (0–20 cm) in 21 coastal wetlands in southeastern China across the tro...

The increasing number of small-hold aquaculture ponds for food production globally has raised concerns of their emission of greenhouse gases (GHGs) such as methane (CH4) and nitrous oxide (N2O). Aeration is commonly applied to improve oxygen supply for the farmed animals, but it could have opposite effects on GHG emission: It may inhibit anaerobic...

Emissions of the potent greenhouse gas nitrous oxide (N2O) from aquaculture remain a large knowledge gap in the global N2O budget. The water column and the sediment of aquaculture ponds present very different environmental conditions, but their relative contributions to N2O production and emission are poorly resolved. We sampled three aquaculture p...

Symsagittifera roscoffensis, an Acoel flatworm that lives within the intertidal zone, was first discovered over a century ago as a "plant animal" due to its symbiotic relationship with the alga Tetraselmis convolutae. Although commonly used as a model organism in biomedical research, there is little information regarding its life history or how env...

Plant invasion and aquaculture activities have drastically modified the landscape of coastal wetlands in many countries, but their impacts on soil organic carbon (SOC) mineralization and greenhouse gas production remain poorly understood. We measured SOC mineralization rate and soil CO2 and CH4 production rates in three habitat types from 21 coasta...

Land reclamation is a major threat to the world's coastal wetlands, and it may influence the biogeochemical cycling of nitrogen in coastal regions. Conversion of coastal marshes into aquaculture ponds is common in the Asian Pacific region, but its impacts on the production and emission of nitrogen greenhouse gases remain poorly understood. In this...

Aquaculture is one of the fastest growing food production sectors in the world, but many of the small-hold operations are poorly assessed for their climate impact. We analyzed the literature data on CO2 and CH4 fluxes from various aquaculture systems in China. The mean fluxes varied in the ranges of − 382.45–551.88 g CO2-C m−2 yr−1 and − 0.03–565.0...

The Gambia is one of the least developed countries in sub-Sahara Africa. In response to the COVID-19 outbreak, the Gambian government implemented a lockdown and various restrictions in 2020, but the impacts on Gambians’ livelihood remained unclear. With the gradual relaxation of the lockdown and restrictions, we were able to conduct the first quest...

Methane emissions from aquatic ecosystems play an important role in global carbon cycle and climate change. Reclamation of coastal wetlands for aquaculture use has been shown to have opposite effects on sediment CH4 production potential and CH4 emission flux, but the underlying reason remained unclear. In this study, we compared sediment properties...

Methane emissions from aquatic ecosystems play an important role in global carbon cycle and climate change. Reclamation of coastal wetlands for aquaculture use has been shown to have opposite effects on sediment CH4 production potential and CH4 emission flux, but the underlying reason remained unclear. In this study, we compared sediment properties...

Some microalgal species can increase their collective size by forming colonies; notable examples are chained colonies in diatoms and Scenedesmus sp., and spherical colonies in Phaeocystis globosa. For a given cell-specific growth rate, chain formation increases collective length quickly to fend off ciliates, but not against tube- and pallium-feedin...

The contribution of dead zooplankton biomass to carbon cycle in aquatic ecosystems is practically unknown. Using abundance data of zooplankton in water column and dead zooplankton in sediment traps in Lake Stechlin, an ecological-mathematical model was developed to simulate the abundance and sinking of zooplankton carcasses and predict the related...

Small-hold aquaculture ponds are widespread in China, but their carbon greenhouse gas emissions are poorly quantified. In this study, we used a carbon budget approach to assess the climate footprint of three earthen aquaculture ponds in southeastern China with the whiteleg shrimp (Litopenaeus vannamei) during the farming period. The main carbon inp...

Widespread conversion of coastal wetlands into aquaculture ponds in the Chinese coastal region often results in degradation of the wetland ecosystems, but its effects on sediment's potential to produce greenhouse gases remain unclear. Using field sampling, incubation experiments and molecular analysis, we studied the sediment CH4 production potenti...

Raman spectroscopy has been commonly used in materials science to detect chemicals. Based on inelastic scattering of light after incident photons interact with a molecule, it has high potential for non-destructive detection of specific contaminants in living biological specimens. The increasing use of carbon nanotubes (CNTs) increases its chance to...

Zoothamnium intermedium is an obligate epibiont ciliate and has been found in a diverse array of hosts and environments. Different studies have reported conflicting distribution patterns and host preferences, even though studies in Chesapeake Bay have suggested that the ciliate has a strong host specificity for two calanoid copepod species. We exam...

While Asia is projected to be one of the major nitrous oxide (N2O) sources in the coming decades, a more accurate assessment of N2O budget has been hampered by low data resolution and poorly constrained emission factor (EF). Since urbanized coastal reservoirs receive high nitrogen loads from diverse sources across a heterogeneous landscape, the use...

Aquaculture can cause serious environmental pollution in the coastal zone. The construction of nutrient budget can provide a scientific basis for understanding the fate of nutrients in the aquaculture systems to facilitate sustainable aquaculture management. In this study, we characterized the nitrogen (N) and phosphorus (P) budgets of coastal land...

Small-scale aquaculture operation is increasing rapidly in the world, particularly in developing countries, but the greenhouse gas (GHG) dynamics and fluxes from small aquaculture ponds are still poorly assessed. In this study, dissolved concentrations and fluxes of CO2 and CH4 were determined in three coastal earthen shrimp ponds over one whole ye...

Coastal reservoirs are widely regarded as a viable solution to the water scarcity problem faced by coastal cities with growing populations. As a result of the accumulation of anthropogenic wastes and the alteration of hydroecological processes, these reservoirs may also become the emission hotspots of nitrous oxide (N2O). Hitherto, accurate global...

A B S T R A C T Static floating chambers (FCs) are the conventional method to measure CH4 fluxes across the water-air interface in ponds, while thin boundary layer (TBL) modelling is increasingly used to estimate CH4 fluxes. In this study, both FCs measurements and TBL models of gas transfer velocity were used to determine CH4 evasion from aquacult...

Microalgae are the foundation of aquatic food webs. Their ability to defend against grazers is paramount to their survival, and modulates their ecological functions. Here, we report a novel anti-grazer strategy in the common green alga Chlorella vulgaris against two grazers, Daphnia magna and Simocephalus sp. The algal cells entered the brood chamb...

Recent discovery of methane (CH4) production in oxic waters challenges the conventional understanding of strict anoxic requirement for biological CH4 production. High-resolution field measurements in Lake Stechlin, as well as incubation experiments, suggested that oxic-water CH4 production occurred throughout much of the water column and was associ...

Recent discovery of oxic methane production in sea and lake waters, as well as wetlands, demands rethinking of the global methane cycle and re-assessment of the contribution of oxic waters to atmospheric methane emission. Here we analysed system-wide sources and sinks of surface-water methane in a temperate lake. Using a mass balance analysis, we s...

Understanding global warming effects on marine zooplankton is key to proper management of marine resources and fisheries. This is particularly urgent for Japan where the coastal water temperature has been increasing faster than the global average over the past decade. Conventional sampling and monitoring programmes, by ignoring the in situ vital st...

Using detailed data of live/dead compositions, along with stage durations and molting rates, we derived, for the first time, both predatory and non-predatory mortality rates of the dominant copepod species within the Humboldt Current System and examined their relationships with environmental factors. [Please contact me for PDF]

The oligotrophic subtropical gyre covers a vast area of the Atlantic Ocean. Decades of time-series monitoring have generated detailed temporal information about zooplankton species and abundances at fixed locations within the gyre, but their live/dead status is often omitted, especially in the dynamic subtropical convergence zone (STCZ) where the w...

Grazer-induced colony formation as a defense strategy in microalgae such as Scenedesmus species has been widely reported, but the associated costs and reversibility of the colonies are rarely studied. We experimentally showed that Scenedesmus obliquus formed chained colonies in the presence of a predator, including predators separated from the alga...

The European and American eels spawn in the subtropical convergence zone (STCZ) in the Sargasso Sea, a dynamic and relatively productive area that is strongly influenced by front and eddy formations and subducted high-saline water masses. To understand how the physical and biological environments may affect the early life history of eels, we conduc...

Chaoborus spp. (phantom midge) are prevalent in eutrophic inland waters. In Lake Soppen, Switzerland, C. flavicans larvae diurnally migrate between the methane-rich, oxygen-depleted hypolimnion and sediments, and the methane-poor, oxygen-rich epilimnion. Using a combination of experiments and system modelling, this study demonstrated that the larva...

Zooplankton populations can at times suffer mass mortality due to non-predatory mortality (NPM) factors, and the resulting carcasses can be captured by sediment traps to estimate NPM rate. This approach assumes sinking to be the primary process in removing carcasses, but in reality, carcasses can also be removed by ingestion, turbulent mixing and m...

Maryland Coastal Bays differ in hydrography from river-dominated estuaries because of limited freshwater inflow from tributary creeks and more marine influence. Consequently, the copepod community structure may be different from that of the coastal ocean and river-dominated estuaries in the mid-Atlantic region. A 2-year study was conducted to descr...

Hypolimnetic oxygen demand in lakes is often assumed to be driven mainly by sediment microbial processes, while the role of Chaoborus larvae, which are prevalent in eutrophic lakes with hypoxic to anoxic bottoms, has been overlooked. We experimentally measured the respiration rates of C. flavicans at different temperatures yielding a Q10 of 1.44–1....

Diurnally-migrating Chaoborus spp. reach populations of up to 130,000 individuals m−2 in lakes up to 70 meters deep on all continents except Antarctica. Linked to eutrophication, migrating Chaoborus spp. dwell in the anoxic sediment during daytime and feed in the oxic surface layer at night. Our experiments show that by burrowing into the sediment,...

In Wales, the barrel jellyfish Rhizostoma octopus is commercially harvested to produce high-value medical grade collagen. Although the fishery is presently not regulated, there are concerns how it may affect the leatherback turtle (Dermochelys coriacea), which preys on R. octopus in local waters. We combined monitoring data and morphometric and wei...

Active methane production in oxygenated lake waters challenges the long-standing paradigm that microbial methane production occurs only under anoxic conditions and forces us to rethink the ecology and environmental dynamics of this powerful greenhouse gas. Methane production in the upper oxic water layers places the methane source closer to the air...

Copepods are exposed to a high non-predatory mortality and their decomposing carcasses act as microniches with intensified microbial activity. Sinking carcasses could thereby represent anoxic microenvironment sustaining anaerobic microbial pathways in otherwise oxic water columns. Using non-invasive O2 imaging, we document that carcasses of Calanus...

Mortality is a main driver in zooplankton population biology but it is poorly constrained in models that describe zooplankton population dynamics, food web interactions and nutrient dynamics. Mortality due to non-predation factors is often ignored even though anecdotal evidence of non-predation mass mortality of zooplankton has been reported repeat...

Intensive sampling at the coastal waters of the central Red Sea during a period of thermal stratification, prior to the main seasonal bloom during winter, showed that vertical patches of prokaryotes and microplankton developed and persisted for several days within the apparently density uniform upper layer. These vertical structures were most likel...

An unusual characteristic of the cosmopolitan haptophyte Phaeocystis globosa is its ability to form colonies of strikingly large size-up to 3 cm in diameter. The large size and the presence of a mucoid envelope are believed to contribute to the formation of dense blooms in Southeast Asia. We collected colonies of different sizes in shallow coastal...

Exchange of the greenhouse gases carbon dioxide (CO2) and methane (CH4) across inland water surfaces is an important component of the terrestrial carbon (C) balance. We investigated the fluxes of these two gases across the surface of oligotrophic Lake Stechlin using a floating chamber approach. The normalized gas transfer rate for CH4 (k600,CH4) wa...

The seasonality of abundance and live/dead compositions of copepods was studied in the northeastern Mediterranean Sea. Zooplankton, chlorophyll-a, and PO4 sampling was performed on a monthly basis from March 2006 to February 2007 at both a coastal station and an open water station. At the coastal station, high phytoplankton biomass was driven by PO...

Zooplankton provide microhabitats for bacteria, but factors which influence zooplankton-associated bacterial abundance are not well known. Through a year-long field study, we measured the concentration of free-living bacteria and bacteria associated with the dominant mesozooplankters Acartia tonsa and Balanus sp. Free-living bacteria peaked in the...

Short-lived, high-intensity turbulence in aquatic environments—or episodic turbulence—has been shown to cause mortality in zooplankton, but its effects on marine phytoplankton have rarely been investigated. Episodic turbulence derives from anthropogenic and natural causes such as boat propellers, strong winds, and breaking waves. This study focused...

Mesozooplankton provide oxic and anoxic microhabitats for associated bacteria, whose carbon substrate usage activities complement those of the ambient bacteria. The metabolic profiles of bacterial communities associated with the calanoid copepod Acartia tonsa under aerobic and anaerobic conditions were examined in comparison with phytoplankton-asso...

The presence of zooplankton swimmers and carcasses in sediment trap samples has long been a concern in particle flux studies. We successfully developed a protocol using the vital stain Neutral Red to distinguish between copepod swimmers and carcasses in conventional cylindrical sediment traps. Swimmers were stained red whereas carcasses were pale o...

Zooplankton carcasses are ubiquitous in marine and freshwater systems, implicating the importance of non-predatory mortality, but both are often overlooked in ecological studies compared with predatory mortality. The development of several microscopic methods allows the distinction between live and dead zooplankton in field samples, and the reporte...

Zooplankton support distinct bacterial communities in high concentrations relative to the surrounding water, but little is known about how the compositions and functionalities of these bacterial communities change through time in relation to environmental conditions. We conducted a year-long field study of bacterial communities associated with comm...

The cosmopolitan alga Phaeocystis globosa forms large blooms in shallow coastal waters off the Viet Nam coast, which impacts the local aquaculture and fishing industries substantially. The unusual feature of this alga is that it forms giant colonies that can reach up to 3 cm in diameter. We conducted experiments designed to elucidate the ecophysiol...

The widely reported paradox of methane oversaturation in oxygenated water challenges the prevailing paradigm that microbial methanogenesis only occurs under anoxic conditions. Using a combination of field sampling, incubation experiments, and modeling, we show that the recurring mid-water methane peak in Lake Stechlin, northeast Germany, was not de...

Quantifying in situ copepod abundances is one of the most fundamental needs in copepod ecological research. Conventional field sampling does not distinguish between live and dead copepods in samples. Corollary to this oversight is that predation is often assumed to be the dominant cause of copepod mortality to the extent that non-predatory mortalit...

Microorganisms such as Bacteria and Archaea play important roles in the Arctic food web and biogeochemical cycles. Nevertheless, knowledge of microbial community composition in Greenland waters is scarce, and information on microorganisms associated with Arctic zooplankton species is virtually non-existent. We compared free-living microbial communi...

Dimethylsulfoniopropionate (DMSP) is a ubiquitous methylated compound in the ocean and a precursor of the climatically active gas dimethyl sulfide (DMS). Copepods have been shown to contain DMSP-consuming bacteria (DCB) in their bodies, which could exploit DMSP ingested by the copepods and attain fast growth. We compared the DCB abundances associat...

Harmful algal blooms (HABs) affect coastal waters worldwide and very often lead to the disruption of seafood harvesting and commercial activities, because of po-tential hazards to human health associated with the consumption of contaminated mussels, crustaceans and fish. HAB events are frequently caused by outbreaks of toxin-producing dinoflagellat...

Ciliate epibionts associated with crustacean zooplankton are widespread in aquatic systems, but their ecological roles are little known. We studied the occurrence of ciliate epibionts on crustacean zooplankton in nine German lakes with different limnological features during the summer of 2011. We also measured the detachment and re-attachment rates...

Using the carcass sinking rate and density determined in laboratory for several freshwater zooplankton species, we developed a model of zooplankton carcass sinking as affected by turbulence and stratification. The model was subsequently used to estimate the residence time of zooplankton carcasses in the water column of Lake Stechlin, a typical temp...

The prevailing paradigm in aquatic science is that microbial methanogenesis happens primarily in anoxic environments. Here, we used multiple complementary approaches to show that microbial methane production could and did occur in the well-oxygenated water column of an oligotrophic lake (Lake Stechlin, Germany). Oversaturation of methane was repeat...

Hydrography and copepod abundances (Acartia tonsa, Eurytemora affinis, and nauplii) were regularly monitored for 2years in sub-estuaries of the lower Chesapeake Bay. Copepod vital status was determined using neutral red. Abundances of A. tonsa copepodites and nauplii peaked in late summer and were related to water temperature. E. affinis was presen...

In order to assess the potential responses of Greenland's coastal ecosystems to future climate change, we studied the hydrography and distribution of metazooplankton, along a transect from the slope waters beyond Fyllas Banke to the inner part of Godthabsfjord, West Greenland, in July and August 2008, and estimated feeding rates for some of the lar...

Using 2 yr of field data on the abundances of live and dead planktonic copepod nauplii and Acartia tonsa copepodites from the lower Chesapeake Bay, we evaluated the accuracy of calculated mortality rates and modeled population dynamics. Copepod mortality rates were estimated from field data both before and after removal of carcasses from abundance...

The environmental conditions inside the gut of Calanus hyperboreus and C. glacialis were measured with microelectrodes. An acidic potential hydrogen (pH) gradient was present in the gut of C. hyperboreus, and the lowest pH recorded was 5.40. The gut pH of a starved copepod decreased by 0.53 after the copepod resumed feeding for a few hours, indicat...