Flow-through Aquarium System Research Articles

Stability of a dominant sponge-symbiont in spite of antibiotic-induced microbiome disturbance.

Marine sponges are known for their complex and stable microbiomes. However, the lack of a gnotobiotic sponge-model and experimental methods to manipulate both the host and the microbial symbionts currently limit our mechanistic understanding of sponge-microbial symbioses. We have used the North Atlantic sponge species Halichondria panicea to evaluate the use of antibiotics to generate gnotobiotic sponges. We further asked whether the microbiome can be reestablished via recolonization with the natural microbiome. Experiments were performed in marine gnotobiotic facilities equipped with a custom-made, sterile, flow-through aquarium system. Bacterial abundance dynamics were monitored qualitatively and quantitatively by 16 S rRNA gene amplicon sequencing and qPCR, respectively. Antibiotics induced dysbiosis by favouring an increase of opportunistic, antibiotic-resistant bacteria, resulting in more complex, but less specific bacteria-bacteria interactions than in untreated sponges. The abundance of the dominant symbiont, Candidatus Halichondribacter symbioticus, remained overall unchanged, reflecting its obligately symbiotic nature. Recolonization with the natural microbiome could not reverse antibiotic-induced dysbiosis. However, single bacterial taxa that were transferred, successfully recolonized the sponge and affected bacteria-bacteria interactions. By experimentally manipulating microbiome composition, we could show the stability of a sponge-symbiont clade despite microbiome dysbiosis. This study contributes to understanding both host-bacteria and bacteria-bacteria interactions in the sponge holobiont.

Secondary calcification and dissolution respond differently to future ocean conditions

Abstract. Climate change threatens both the accretion and erosion processes that sustain coral reefs. Secondary calcification, bioerosion, and reef dissolution are integral to the structural complexity and long-term persistence of coral reefs, yet these processes have received less research attention than reef accretion by corals. In this study, we use climate scenarios from RCP 8.5 to examine the combined effects of rising ocean acidity and sea surface temperature (SST) on both secondary calcification and dissolution rates of a natural coral rubble community using a flow-through aquarium system. We found that secondary reef calcification and dissolution responded differently to the combined effect of pCO2 and temperature. Calcification had a non-linear response to the combined effect of pCO2 and temperature: the highest calcification rate occurred slightly above ambient conditions and the lowest calcification rate was in the highest temperature–pCO2 condition. In contrast, dissolution increased linearly with temperature–pCO2 . The rubble community switched from net calcification to net dissolution at +271 μatm pCO2 and 0.75 °C above ambient conditions, suggesting that rubble reefs may shift from net calcification to net dissolution before the end of the century. Our results indicate that (i) dissolution may be more sensitive to climate change than calcification and (ii) that calcification and dissolution have different functional responses to climate stressors; this highlights the need to study the effects of climate stressors on both calcification and dissolution to predict future changes in coral reefs.

In situ short-term growth rates of a cold-water coral

Cold-water corals are known to grow much slower than their tropical counterparts. However, this assumption is mainly based on laboratory measurements exposing specimens to conditions that differ from their natural environments. The cosmopolitan scleractinian Desmophyllum dianthus forms dense banks below 18 m in northern Patagonia, Chile. So as to measure in situ growth rates of this cold-water coral, specimens were collected from two sites, weighed and deployed on holders in their natural headlong orientation at the respective collecting site. Corals exhibited a calcium carbonate (CaCO3) mass increase of 5.44 ± 3.45 (mg (cm2 projected calyx area)–1 day–1) after 2 weeks, equivalent to a mass gain of 0.25 ± 0.18 s.d. % day–1. In comparison, D. dianthus specimens from the same collection sites maintained in an on-site flow-through aquarium system showed lower growth rates that were third of the in situ rates. In situ CaCO3 precipitation of D. dianthus extrapolated for 1 year (kg m2 year–1) displays the same order of magnitude as reported for massive growing tropical scleractinians, e.g. Porites sp.

Effects of two sediment types on the fluorescence yield of two Hawaiian scleractinian corals

This study used non-invasive pulse-amplitude modulated (PAM) fluorometry to measure the maximum fluorescence yield (F(v)/F(m)) of two Hawaiian scleractinian coral species exposed to short-term sedimentation stress. Beach sand or harbor mud was applied to coral fragments in a flow-through aquarium system for 0-45 h, and changes in F(v)/F(m) were measured as a function of sediment type and length of exposure. Corals were monitored for up to 90 h to document recovery after sediment removal. Sediment deposition significantly decreased F(v)/F(m) in both species and was a function of sediment type and time. Corals that received sediment for 30 h or more had the greatest reduction in yield and exhibited little recovery over the course of the experiment. Harbor mud caused a greater reduction in Porites lobata yield than beach sand, whereas both sediment types had equally deleterious effects on Montipora capitata. Colony morphology and sediment type were important factors in determining yield reduction--P. lobata minimized damage from coarse sand grains by passive sediment rejection or accumulation in depressions in the skeleton, and fluorescence yield decreased most in corals exposed to sticky harbor mud or in colonies with flattened morphologies. Species-specific differences could not be tested due to differences in colony morphology and surface area.

Interaction between water flow and oxygen deficiency on growth in the infaunal brittle star Amphiura filiformis (Echinodermata: Ophiuroidea)

Interactions between ‘oxygen concentration’ (normoxia: >80% oxygen saturation, and hypoxia: 18% oxygen saturation) and ‘water flow velocity’ (low: 0.1 cm s −1, and moderate: 0.5 cm s −1) were studied on growth rates in the brittle star Amphiura filiformis in a flow-through aquaria system. Effects of ‘sublethal predation’ on growth rates were investigated as ‘number of amputated arms’ (1 and 3 arms) and ‘amputation of the disk’. A significant interaction between oxygen concentration and water flow velocity was observed in mean arm regeneration rate, but in both flow velocities higher mean arm regeneration rates were observed in normoxia compared to hypoxia. In hypoxia a positive response in arm regeneration rate was observed in moderate flow compared to low flow velocity. In normoxia, however, no response to flow velocity was observed. The latter observation indicates that Amphiura filiformis is able to maintain the ventilation of the burrow at low flow velocities, but in low oxygen concentrations hydrodynamic forces seem to affect growth. A significant interaction between oxygen concentration and disk amputation was observed in both arm and disk regeneration rates, indicating that the disk is the major organ for gas exchange in this species. The number of arms amputated, however, did not affect mean arm regeneration rate. The results obtained in this study suggest that the secondary production in subtidal infaunal populations could be negatively affected by low oxygen concentrations and that this response is even more negative in combination with low flow velocities in the near-bottom water.

Long-term toxicity of zinc to bacteria and algae in periphyton communities from the river Göta Älv, based on a microcosm study

This study aims to clarify the relation between pollution-induced community tolerance (PICT), community structure and net production in periphyton communities exposed to environmentally realistic concentrations of zinc and to determine levels of no-effect (NEC). Therefore, periphyton communities from a relatively uncontaminated river (Göta Älv, Sweden) were exposed to zinc during 4 weeks in a flow-through aquaria system. PICT was estimated as the increase in EC 50 for the short-term inhibition of photosynthesis and thymidine incorporation. Community structure was measured as species richness and Bray–Curtis similarity index, and biomass as dry weight and chlorophyll a. NEC values were estimated as the intercept between a regression line and a control base line. NEC values for biomass and biomass dependent variables were 0.12–0.42 μM which implies that there may be many rivers affected by zinc. However, the PICT response and marked changes in community species composition were found only at much higher concentrations (9.7 μM). We hypothesise that this discrepancy in effect concentrations between biomass-dependent variables and other structure-related variables (including PICT) is due to an interaction between zinc and phosphorus leading to nutrient depletion. An indirect toxic effect on biomass due to nutrient deficiency should not be detectable as an increased zinc tolerance.

Effects of hypoxia and organic enrichment on growth of the brittle stars Amphiura filiformis (O.F. Müller) and Amphiura chiajei Forbes

Effects of oxygen concentration (normoxia: >8.0 mg O 2 l −1 and hypoxia: 1.8–2.2 mg O 2 l −1) and organic enrichment (control: 0 g C m −2, medium: 27 g C m −2 and high: 55 g C m −2) were studied on arm regeneration rate in two infaunal brittle star species, Amphiura filiformis and Amphiura chiajei, during a two-month period in a flow-through aquaria system. In both species arm regeneration rates were significantly higher in organic enriched aquaria compared to control aquaria. Hypoxia significantly decreased the arm regeneration rate in Amphiura filiformis but did not affect the rate in Amphiura chiajei. The results suggest that Amphiura filiformis is more sensitive than Amphiura chiajei to hypoxia. Analyses on growth and energy allocation in Amphiura filiformis were carried out on the main factors oxygen concentration, organic enrichment, and amount of arm loss that simulated sublethal predation. The effect of sublethal predation was measured as growth of one or three arms that were amputated at the start of the experiment. Significant interactions between sublethal predation and organic enrichment, and oxygen concentration and organic enrichment, were observed for arm regeneration in Amphiura filiformis. Arm regeneration rate in specimens with one arm amputated differed significantly between the three treatments of organic enrichment, but no difference was found in specimens with three arms amputated. In normoxia, arm regeneration rates increased in both medium and high organic load compared to control. However, in hypoxia, a positive growth response was only observed in the treatment medium organic load. At the termination of the experiment, dry mass of disks was significantly higher in specimens with one regenerated arm compared with specimens with three regenerated arms. The response of Amphiura filiformis to sublethal predation indicates also an ability to allocate energy between disk growth (reproductive investment) and arm regeneration (somatic growth).

Pollution-induced community tolerance (PICT) in periphyton communities established under tri- n-butyltin (TBT) stress in marine microcosms

The environmental problem of the antifouling agent tri- n-butyltin (TBT) was recognized during the 1980's and the use of TBT on pleasure crafts was banned in several countries. Marine periphyton were established in a flow-through aquaria system under TBT stress. Pollution-induced community tolerance (PICT) was quantified, in a short-term test for inhibition of photosynthesis, and compared to effects on biomass and community structure. Community structure was measured by diatom species richness, Jaccard similarity index, Bray-Curtis dissimilarity index and evaluated by linear regression and multidimensional scaling (MDS) techniques. The aim was to (1) determine a no effect level for marine periphyton communities under ecologically realistic conditions (2) validate PICT against other long-term effect indicators (3) confirm, with a controlled experiment, the TBT effect thresholds indicated by PICT studies in the field. We found that TBT alone indeed was able to cause the same kind of effects on periphyton that earlier have been detected in periphyton from contaminated ecosystems and that the effects occur at concentrations in water higher than 0.5 nM TBT. The agreement between TBT effects in field and in the microcosm system implies that the system is sufficiently realistic in yielding ecologically relevant information. Effect indicators such as periphyton photosynthesis and net production were found to be less sensitive than PICT and community structure.

Bioconcentration and elimination of bis(tributyltin)oxide (TBTO) and triphenyltin chloride (TPTC) in several marine fish species

Pagrus major, Mugil cephalus and Rudarius ercodes were exposed to bis(tributyltin)oxide (TBTO) and triphenyltin chloride (TPTC) for 8 weeks in a flow-through aquarium system. The bioconcentration factors (BCFs) of TBTO and TPTC and the elimination rate constant of TBTO for these fish were determined. The BCF of TBTO ranged from 2400 to 11,000 depending on the fish species and the concentration in the rearing seawater. Out of the three, P. major had the smallest elimination rate constant (0.024 day −1) and bioconcentrated the largest amount of TBTO (BCF: 9400–11,000). On the other hand, the BCF of TPTC of the two fish species examined was similar: 3100–3300 for P. major and 4100 for R. ercodes. These BCFs of TBTO and TPTC of P. major were larger than the values previously reported. TBTO and TPTC were the least accumulated in muscle among the tissues and organs of P. major examined, and no correlation was found between the lipid content and the accumulated TBT or TPT content.

Pattern of cotolerance in marine periphyton communities established under arsenate stress

Arsenate-tolerant marine periphyton communities established under arsenate stress in a flow-through aquarium system, were investigated for cotolerance to various inhibitors of photosynthesis. A short-term test system for inhibition of periphyton photosynthesis was used to quantify the community tolerance levels. Preexposure to arsenate at 10 μM increased arsenate tolerance > 16,000-fold compared to control communities established at background levels of arsenate. A substantial cotolerance was observed only for thiophosphate which is a phosphate analog uncoupler of photophosphorylation with a mode of action similar to that of arsenate. For the uncouplers CCCP (carbonyl cyanide m-chloro-phenylhydrazone) and Primene JMT (a primary amine with a branched C 18–C 22 aliphatic chain), the inhibitor of photosynthetic electron transport DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) and arsenite, there was a general tendency for a small cotolerance, although for Primene JMT and DCMU an increased sensitivity was some-times observed. The general increase in tolerance was however quantitatively insignificant compared to the specific cotolerance observed for thiophosphate, suggesting that the mode of action and tolerance mechanisms are similar for arsenate and thiophosphate, and most likely related to their phosphate analogy. We suggest that significant cotolerance is not ubiquitous nor common in periphyton, and that the emerging cotolerance pattern may be indicative of the toxicity and tolerance mechanisms.

数種淡水魚におけるｐ，ｐ′‐ＤＤＴの初期代謝経路の比較

Eleven freshwater fishes were kept in a flow-through aquarium system (FAS) and in a closed aquarium system (CAS) after intraperitoneal injection of p, p'-DDT (DDT). Concentrations of DDT, p, p'-DDE (DDE), p, p'-DDD and p, p'-DDT-OH in the whole body and in the CAS were determined.Japanese barbel, Japanese dace and char rapidly converted DDT into DDE only, and the ΣDDT in the whole CAS (consisted of fish, aquarium and rearing water) were nearly equal to the original DDT, suggesting only one initial metabolic pathway (IMP) changing rapidly the DDT into DDE. In crucian carp, loach, Japanese sculpin, floating goby and catfish, slight increase of only DDE were observed, and the ΣDDT in their whole CAS almost corresponded to the DDT injected, suggesting only one IMP converting slowly from DDT to DDE. The DDT in grass carp was immediately cleared and only DDE increased without delay, and the ΣDDT in the whole CAS was about 50% of the original DDT. In bluegill, only DDE gradually increased with clearance of DDT, and the ΣDDT in the whole CAS was about 85% of the original DDT. These results suggested that grass carp had IMP converting quickly from DDT to DDE and other metabolites undetermined and that bluegill had a similar pathway, but it was slower. Japanese eel might not have clear IMP, considering the fact that no metabolite was detected and the DDT injected remained completely in the whole CAS.

Validity of an Ecotoxicological Test System: Short-Term and Long-Term Effects of Arsenate on Marine Periphyton Communities in Laboratory Systems

Periphyton communities were established on glass substratum in the Gullmar Fjord (Sweden) and their sensitivity to arsenate was determined with short-term photosynthesis experiments. The study was done in May 1984 when phosphate levels were low. A 1-h exposure to arsenate gave IC20 (concentration required to inhibit photosynthesis by 20%) values of 0.4 μM. Communities established indoors in a flow-through aquaria system were substantially different from the fjord communities in terms of structure and biomass, although photosynthesis showed a similar sensitivity (IC20 = 0.6 μM). To explore the validity of this short-term ecotoxicological test system, we used a set of indoor, flow-through aquaria to study long-term effects (3 wk) on communities established under arsenate stress. Arsenate was added continuously at 0.1–10 μM above background levels (7 nM). Species composition as well as carbon, nitrogen, and chlorophyll a content of the communities were affected at 0.2–0.8 μM (IC20). This is in good agreement with the sensitivity of the short-term test. We conclude that inhibition of the physiological parameter photosynthesis is relevant information for the understanding of ecological events caused by arsenate stress in the periphyton communities. At least for effects of arsenate, the short-term metabolic test system can be used for valid predictions of gross changes in periphyton community structure and production. Comparison with arsenic levels in polluted coastal areas of Sweden lead to the conclusion that periphyton communities may be affected, particularly when phosphorus levels are low.

An estimate of the dietary calcium requirement of fingerling Tilapia aurea reared in calcium-free water

Seven isocaloric and isonitrogenous semi-purified diets which contained graded levels of calcium ranging from 0.17 to 3.20% were fed to fingerling Tilapia aurea for a period of 11 weeks. The fish were maintained in a flow-through aquarium system supplied with calcium-free well water. Growth, feed conversion and bone composition data indicated that between 0.17 and 0.65% dietary calcium was adequate for optimum growth and normal bone mineralization.