Linking microbial communities and macrofauna functional diversity with benthic ecosystem functioning in shallow coastal sediments, with an emphasis on nitrifiers and denitrifiers

Shallow coastal habitats represent some of the most valued ecosystems supporting complex communities of benthic organisms, delivering diverse ecosystem services. Cumulative activities of the benthic fauna affect the physical and chemical conditions of their environment and determine the rate of processes and benthic ecosystem functioning in coastal areas. However, excessive human use of the coastal zone puts extensive pressure on coastal ecosystems leading to biodiversity loss and habitat destruction. Therefore, it is essential to implement Ecosystem-Based Management (EBM) to ensure the protection of coastal resources whilst increasing the efficiency of their uses. Such EBM needs to be based on solid scientific evidence, including a detailed understanding of the link between biodiversity and ecosystem functioning.Macrofaunal assemblages have been shown to impact microbial-mediated nitrogen cycling processes in marine sediments through their role in affecting the physical and chemical conditions as they affect the exchange processes across the sediment-water interface. However, how the functional traits of macro-organisms, through the interactions with micro-organisms, affect microbial-mediated ecosystem functioning is still not fully understood. This PhD thesis aims to investigate the effect of macrofauna (at the community and species level) on benthic microbial communities (total bacterial and archaeal communities and specific functional groups, nitrifiers and denitrifiers) and the N-cycle processes mediated by them (nitrification and denitrification). The nitrogen cycle is one of the most important biogeochemical cycles in ecosystems. It provides nitrogen as an important component for all living cells and for primary production. It also counteracts eutrophication in the coastal marine area; it also releases back the biologically useful nitrogen into the atmosphere by converting it into gaseous compounds in both terrestrial and marine ecosystems (Canfield et al., 2005)

Biotechnique of rearing beluga (H.huso) using brackishwater of the Caspian Sea (different densities and water flow)

This study was conducted at the Applied Research Station for Sturgeon Culture (Chaboksar site) and was supported by the Iranian Fisheries Research Organization in order to obtain the bio technique for Huso huso culture in brackish water from the Caspian Sea. The effects of stocking density and water flow at the inlet of brackish water was studied for a period of 4 years using 4 weight classes and the results obtained were compared with those obtained from the culture of H. huso in freshwater. Huso huso in four weight classes of 3-20 g, 20-200 g, 325-1000 g and 1000-3000 g were stocked at stocking densities between 350 g to 15 kg m^-2. The effect of water flow in rearing tanks was studied in weight classes 30- 2700 g. In the weight class 3-20 g, highest growth was recorded in H. huso stocked at 1000 g m^-2 in brackish water which was significantly higher (P<0.5) than that recorded in freshwater suggesting the advantage of rearing H. huso in brackish water at improved density of 1000 g m^-2. Results obtained from total length in juvenile H. husoconform to these results. It may therefore be concluded that in the weight class 3-20 g, stocking density of 1000 g m^-2 is not a limiting factor on growth in juvenile H. huso. Low specific growth rate (SGR) was reported with a stocking density of 1500 g m^-2 in freshwater which was not significantly different from that in brackish water. Hence rearing juvenile H. huso in brackish water at high densities (1500 g m^-2) is preferred to rearing in freshwater as H. huso is more capable of adapting to stressful conditions of stocking density in brackish water. Similar trends were observed for percentage body weight increase (BWI%) showing the advantage of using a stocking density of 1000 g m^-2 in brackish water. Production in different groups showed variations depending on stocking density biomass. Condition factor was low when H. huso was reared in freshwater at a stocking density of 1500 g m^-2. Similarly CVw was low in the experimental group reared at a density of 500 g m-2 in brackish water, while CVtl in the group reared at 1500 g m^-2 in brackish water was low. The calculated value for CVw/tl was low with stocking density of 500 g m^-2 in brackish water and freshwater. Final body weight and growth indices in the 20-200 g weight class in the experimental group using 1000 g m^-2 in brackish water were higher than that in freshwater. Similarly growth indices and final body weight of juvenile H. huso at 2000 and 1500 g m^-2 stocking densities were higher than the values obtained with similar stocking densities in freshwater. SGR and growth rate (GR) of H. huso at stocking density of 1500 g m^-2 was significantly higher in brackish water than that in freshwater. Comparison of results obtained from weight and total length in weight classes 325-560 g showed that until they reach a weight of 560 g, stocking density of 1.3 kg m^-2 in brackish water is preferred to the densities 2.6, 3.9 and 5.2 kg m^-2. Comparison of results indicate that in the weight class 325-560 g, better results are obtained when juvenile H. huso are reared in brackish water at densities of 1.3, 2.6 and 3.9 kg m^-2 as compared to that obtained from the use similar densities in freshwater. Statistical analysis of SGR indicates that stocking densities up to 2.6 kg m^-2 do not limit growth. Also it was also evident from the analyses of SGR and FCR that stocking density of 5.2 kg m^-2 is not considered suitable for juvenile H. huso in the weight class 325-560 g. On the basis of results obtained for SGR, GR and FCR it maybe concluded that up to the 760 g weight class, stocking densities of 1.3 and 2.6 kg m^-2 were statistically better than other densities studied. Moreover rearing juvenile H. huso at these stocking densities in brackish water also proved better than that in freshwater. In the weight class 650-1000 g, stocking fish at densities of 2.6 -10 kg m^-2 in brackish water did not seem to affect final body weight, total length and SGR. At stocking densities 5.1 and 7 kg m^-2, GR for juvenile H. huso in brackish water were significantly higher than that obtained in freshwater using the same stocking densities. Similarly FCR and FE values obtained for juvenile H. huso in this weight class in brackish water were significantly better (P<0.05) than those obtained in freshwater. SGR values obtained at stocking densities 7 and 10 kg m^-2 support these findings. Based on body weight, total length and GR values it may be concluded that stocking density of 10 kg m^-2 does not restrict growth in juvenile H. huso until they reach a body weight of 1000 g. Similarly a stocking density of 7.5 kg m^-2 does not limit growth in juvenile H. huso until they reached a body weight of 1150 g and stocking densities of 5.1 kg m^-2 and 2.6 kg m^-2 do not limit growth in juvenile H. huso until they reach body weights of 1300 and 1500 g, respectively. Rearing H. huso in these weight classes at different stocking densities of 10, 7.5 and 5.1 kg m^-2 in brackish water was significantly better than rearing them in freshwater. Also based on feeding indices (FCR, FE, SGR and GR) in these weight classes, stocking densities of 2.6 and 5.1 kg m^-2 in brackish water were significantly more suitable than other stocking densities studied in the same culture medium. Results obtained from rearing juvenile H. huso at stocking densities of 2.6, 5.1 and 7.5 kg m^-2 in brackish water was significantly better than that obtained in freshwater at the same stocking densities. Based on growth (SGR, BWI) and feeding (FE) indices in the weight class 900-3000 g it is evident that experimental group 5 (with stocking density of 10 kg m^-2 , water flow of 3 L sec^-1) was significantly better (P<0.05) than all other groups studied. It may also be concluded from the results obtained by studying stocking densities and water flow that stocking density of 10 kg m^-2 used for rearing juvenile H. huso in the weight class 900 g until they reach a weight of 3000 g is not a limiting factor on their growth. It was also observed that juvenile H. huso are highly capable of adapting to their environment. The one-way water supply and daily water exchange with different water flow rates ranging from 1 to 6 L sec^-1 yielded similar results. It was clearly evident that a water flow rate of 0.5 L sec^-1 in brackish water and freshwater resulted in significantly lower growth in juvenile H. huso. Highest growth was reported in brackish water with a flow rate of 1.5 and 3 L sec-1. In freshwater, highest growth was recorded with flow rates of 3 L sec^-1. Higher water flow rates improved growth indices in H. huso. Improved condition factor and variable coefficients of weight and total length were observed in experimental groups in brackish water and freshwater, except in the experimental group with a flow rate of 0.5 L sec^-1 in freshwater. In the weight class 530-2000 g, water flow rate of 3 L sec-1 produced higher final weight in juvenile H. huso in freshwater as compared to that in brackish water. Similar results were obtained in freshwater and brackish water with water flow rate of 1.5 L sec^-1. Data on carcass composition of farmed H. huso indicated no significant effect of freshwater and brackish water on protein and lipid levels. In both rearing media, diets were formulated to meet the dietary requirements of H.huso and hence carcass composition conformed to the quality of diets

Influence of food attractants (methionine, lysine and alanine) on sturgeon larvae and fingerlings nutrition

The objective of this study was to determine the influence of food attractants (methionine, lysine and alanine) on growth performance and survival rates of Acipenser percicus larvae and fingerlings during the acclimation period to the formulated diets. A total of 3300 Acipenser percicus larvae and 1500 Acipenser percicus fingerlings with the initial mean weights of 0.4±0.09 (mean±SD) and 1.8±0.3 (mean±SD) g, respectively were randomly distributed into 30 aerated plastic tanks of 30 L capacity for larval stage and 50 L capacity for fingerling stage provided with a water flow rate of 0.2 litre per second. This study was conducted at the International Sturgeon Research Institute for two periods of 62 and 70 days over two years. Nine iso-caloric diets were formulated to contain 0, 1 and 3 % of three amino acids methionine, lysine and alanine. In addition, a diet containing 50 % of plant protein supplemented with 3 % of methionine, lysine and alanine was also formulated to compare the effects of plant-protein-based diet with the experimental diets so as to prepare a cost-effective practical diet for this species. Fish were fed each of the ten experimental diets and a completely randomized design in a 3×3 factorial arrangement was used for the experiment. At the end of the feeding trial, final weight (7.5 ± 0.3 g) in Persian sturgeon larvae fed M3L1A3 diet (3% methionine and alanine and 1% lysine) was significantly higher than those of fish fed the other experimental diets (p≤0.05) and then M1L1A3 diet (1% methionine and lysine and 3% alanine) was significantly better (p≤0.05) than other experimental diets. There were no significant differences (p≥0.05) in final weights among M1L1A1, M3L1A1, M3L3A1, M1L3A3 and M3L3A3 diets, while theses diets showed significant differences in final weight with fish fed plant-protein-based diet (3.2±1 g) and without amino acids supplemented diet (M0L0A0) (3.6± 0.4 g). Based on final weigh obtained from Persian sturgeon fingerlings, there were significant differences (p≤0.05) between M3L3A3 (3% methionine, 3% lysine and 3% alanine) (11.1±3.6g) and M3L1A3 (3% methionine, 1% lysine and 3% alanine) (10.4±3.1g) diets with M1L1A1, M1L3A1, M1L1A3, M0L0A0 and plant-protein-based diets. Results of final weigh in fingerling stage also indicated that there were no significant differences (p≥0.05) among M1L1A1 (7±1.2 g), M3L1A1 (8.6±1.6 g), M1L3A1 (7±0.5 g) and M1L1A3 diets (6.6±1.0 g) with M0L0A0 (5.8±1.8 g) and plant-protein-based diets. Analysis of total length in Persian sturgeon fingerlings indicated that there were no significant differences (p≥0.05) among treatments. The highest total length (12±1.6 cm) was recorded in fish fed M3L1A3 diet. Results obtained from this study revealed that young growing Persian sturgeon has greater requirements for methionine in diet, while lysine and alanine at the levels of 1 and 3% for Persian sturgeon fingerlings and at the level of 3% for larvae stage show the same effects on growth performance. Hence, it may be concluded that the dietary alanine and lysine requirements for sturgeon larvae during the acclimation period to formulated diet is estimated to be more than 1 %. No significant differences were observed in survival rates in sturgeon larvae and fingerlings among treatments

Limited congruence exhibited across microbial, meiofaunal and macrofaunal benthic assemblages in a heterogeneous coastal environment

One of the most common approaches for investigating the ecology of spatially complex environments is to examine a single biotic assemblage present, such as macroinvertebrates. Underlying this approach are assumptions that sampled and unsampled taxa respond similarly to environmental gradients and exhibit congruence across different sites. These assumptions were tested for five benthic groups of various sizes (archaea, bacteria, microbial eukaryotes/protists, meiofauna and macrofauna) in Plymouth Sound, a harbour with many different pollution sources. Sediments varied in granulometry, hydrocarbon and trace metal concentrations. Following variable reduction, canonical correspondence analysis did not identify any associations between sediment characteristics and assemblage composition of archaea or macrofauna. In contrast, variation in bacteria was associated with granulometry, trace metal variations and bioturbation (e.g. community bioturbation potential). Protists varied with granulometry, hydrocarbon and trace metal predictors. Meiofaunal variation was associated with hydrocarbon and bioturbation predictors. Taxon turnover between sites varied with only three out of 10 group pairs showing congruence (meiofauna-protists, meiofauna-macrofauna and protists-macrofauna). While our results support using eukaryotic taxa as proxies for others, the lack of congruence suggests caution should be applied to inferring wider indicator or functional interpretations from studies of a single biotic assemblage

Variable importance of macrofaunal functional biodiversity for biogeochemical cycling in temperate coastal sediments

Coastal marine systems are currently subject to a variety of anthropogenic and climate-change-induced pressures. An important challenge is to predict how marine sediment communities and benthic biogeochemical cycling will be affected by these ongoing changes. To this end, it is of paramount importance to first better understand the natural variability in coastal benthic biogeochemical cycling and how this is influenced by local environmental conditions and faunal biodiversity. Here, we studied sedimentary biogeochemical cycling at ten coastal stations in the Southern North Sea on a monthly basis from February to October 2011. We explored the spatio-temporal variability in oxygen consumption, dissolved inorganic nitrogen and alkalinity fluxes, and estimated rates of nitrification and denitrification from a mass budget. In a next step, we statistically modeled their relation with environmental variables and structural and functional macrobenthic community characteristics. Our results show that the cohesive, muddy sediments were poor in functional macrobenthic diversity and displayed intermediate oxygen consumption rates, but the highest ammonium effluxes. These muddy sites also showed an elevated alkalinity release from the sediment, which can be explained by the elevated rate of anaerobic processes taking place. Fine sandy sediments were rich in functional macrobenthic diversity and had the maximum oxygen consumption and estimated denitrification rates. Permeable sediments were also poor in macrobenthic functional diversity and showed the lowest oxygen consumption rates and only small fluxes of ammonium and alkalinity. Macrobenthic functional biodiversity as estimated from bioturbation potential appeared a better variable than macrobenthic density in explaining oxygen consumption, ammonium and alkalinity fluxes, and estimated denitrification. However, this importance of functional biodiversity was manifested particularly in fine sandy sediments, to a lesser account in permeable sediments, but not in muddy sediments. The strong relationship between macrobenthic functional biodiversity and biogeochemical cycling in fine sandy sediments implies that a future loss of macrobenthic functional diversity will have important repercussions for benthic ecosystem functioning