Carbon Flux in the Temperate Zooxanthellate Sea Anemone Anthopleura aureoradiata

<p>This study investigated the algal density and growth, photophysiology and contribution of algae to animal respiration requirements (CZAR), in the symbiosis between the sea anemone Anthopleura aureoradiata and its dinoflagellate symbionts (zooxanthellae) under field and laboratory conditions. A. aureoradiata was collected during summer and winter on sunny and cloudy days from a rocky shore and mudflat environment. Algal densities displayed a trend of being 2.6 and 1.7 times greater during summer than winter on the mudflat on a sunny and cloudy day respectively. Algal division was asynchronous under field conditions over a daily period, and was 2.1 and 1.3 times greater on the rocky shore and mudflat respectively, during winter than summer on sunny days. Under field conditions, the efficiency and maximum rate of photosynthesis (per cell and per association) as well as respiration rate, were all greater during summer than winter. Cloud cover resulted in a difference in a higher maximum rate of photosynthesis per cell on a sunny day than a cloudy day within summer at Kau Bay. Additionally, these photosynthetic parameters and respiration rate were all greater on the rocky shore than mudflat while the photosynthetic compensation irradiance was greater on the mudflat. The CZAR was greatest on the rocky shore during summer on a sunny day (151%) and was also > 100% on a cloudy day in summer at this same site (129%); on the mudflat the CZAR was greatest during summer on a sunny day (89%). The CZAR was measured to be zero during winter at both sites during winter on cloudy days. Additionally, under laboratory conditions A. aureoradiata was exposed to gradual (GTC) and rapid (RTC) temperature changes. While under GTC and RTC, the algal density did not vary, though higher temperatures led to an increase in algal division. Under both GTC and RTC, the photosynthetic efficiency, maximum photosynthetic rate (per cell and per association) and respiration rate all increased with temperature, however under GTC these parameters all decreased between 32.5 [degrees]C and 35 [degrees] C. Photosynthetic compensation irradiance increased with temperature under both GTC and RTC until 30 [degrees] C, after which respiration exceeded maximum photosynthesis, meaning that photosynthetic compensation did not occur. Furthermore, photosynthetic saturation irradiance increased with temperature and peaked at 15 [degrees] C before declining with temperature under both GTC and RTC. The CZAR under GTC increased with temperature until it peaked at 15 [degrees] C (128%), before decreasing to zero at 30 [degrees] C - 35 [degrees] C. Under RTC, the CZAR was zero for all temperatures except at 10 [degrees] C where it was 25.1%. A CZAR < 100% may suggest that the symbiosis between A. aureoradiata and its zooxanthellae is parasitic under most conditions and at most times of the year. Alternatively, there may be some benefit to the symbiosis due to a competitive advantage over other macro-invertebrate species as a result of carbon translocation from the symbiont providing extra support for reproduction and growth. This study also showed A. aureoradiata to have a wide temperature tolerance reflecting the fluctuating conditions of a variable temperate environment. The wide temperature tolerance of this species suggests that it will tolerate short term (50 - 100 years) increases in ocean temperatures however, the threat beyond this time frame with other factors such as ocean acidification remains to be determined.</p>

Carbon Flux in the Temperate Zooxanthellate Sea Anemone Anthopleura aureoradiata

<p>This study investigated the algal density and growth, photophysiology and contribution of algae to animal respiration requirements (CZAR), in the symbiosis between the sea anemone Anthopleura aureoradiata and its dinoflagellate symbionts (zooxanthellae) under field and laboratory conditions. A. aureoradiata was collected during summer and winter on sunny and cloudy days from a rocky shore and mudflat environment. Algal densities displayed a trend of being 2.6 and 1.7 times greater during summer than winter on the mudflat on a sunny and cloudy day respectively. Algal division was asynchronous under field conditions over a daily period, and was 2.1 and 1.3 times greater on the rocky shore and mudflat respectively, during winter than summer on sunny days. Under field conditions, the efficiency and maximum rate of photosynthesis (per cell and per association) as well as respiration rate, were all greater during summer than winter. Cloud cover resulted in a difference in a higher maximum rate of photosynthesis per cell on a sunny day than a cloudy day within summer at Kau Bay. Additionally, these photosynthetic parameters and respiration rate were all greater on the rocky shore than mudflat while the photosynthetic compensation irradiance was greater on the mudflat. The CZAR was greatest on the rocky shore during summer on a sunny day (151%) and was also > 100% on a cloudy day in summer at this same site (129%); on the mudflat the CZAR was greatest during summer on a sunny day (89%). The CZAR was measured to be zero during winter at both sites during winter on cloudy days. Additionally, under laboratory conditions A. aureoradiata was exposed to gradual (GTC) and rapid (RTC) temperature changes. While under GTC and RTC, the algal density did not vary, though higher temperatures led to an increase in algal division. Under both GTC and RTC, the photosynthetic efficiency, maximum photosynthetic rate (per cell and per association) and respiration rate all increased with temperature, however under GTC these parameters all decreased between 32.5 [degrees]C and 35 [degrees] C. Photosynthetic compensation irradiance increased with temperature under both GTC and RTC until 30 [degrees] C, after which respiration exceeded maximum photosynthesis, meaning that photosynthetic compensation did not occur. Furthermore, photosynthetic saturation irradiance increased with temperature and peaked at 15 [degrees] C before declining with temperature under both GTC and RTC. The CZAR under GTC increased with temperature until it peaked at 15 [degrees] C (128%), before decreasing to zero at 30 [degrees] C - 35 [degrees] C. Under RTC, the CZAR was zero for all temperatures except at 10 [degrees] C where it was 25.1%. A CZAR < 100% may suggest that the symbiosis between A. aureoradiata and its zooxanthellae is parasitic under most conditions and at most times of the year. Alternatively, there may be some benefit to the symbiosis due to a competitive advantage over other macro-invertebrate species as a result of carbon translocation from the symbiont providing extra support for reproduction and growth. This study also showed A. aureoradiata to have a wide temperature tolerance reflecting the fluctuating conditions of a variable temperate environment. The wide temperature tolerance of this species suggests that it will tolerate short term (50 - 100 years) increases in ocean temperatures however, the threat beyond this time frame with other factors such as ocean acidification remains to be determined.</p>

Influence of light quality on Chlorella growth, photosynthetic pigments and high-valued products accumulation in coastal saline-alkali leachate

Using saline-alkali leachate to cultivate microalgae is an effective way to realize the utilization of wastewater and alleviate the shortage of water resources. Light source is usually used as an optimized parameter to further improve the cultivation efficiency of microalgae. In this work, the influence of light qualities on the growth and high-valued substances accumulation of Chlorella sp. HQ in coastal saline-alkali leachate were investigated. The specific growth rate of Chlorella in coastal saline-alkali leachate was 0.27–0.60 d−1. At the end of cultivation, the algal density under blue light reached 8.71 ± 0.15 × 107 cells·mL−1, which was significantly higher than the other light groups. The lipid content in the biomass was 29.31–62.95%, and the highest lipid content and TAGs content were obtained under red light and blue-white mixed light, respectively. Percentages of total chlorophylls (0.81–1.70%) and carotenoids (0.08–0.25%) were obtained in the final biomass of the coastal saline-alkali leachate. In addition, the contents of photosynthetic pigments and three high-valued products under mixed light were higher than those of monochromatic light, and the protein, total sugar and starch content under blue-red mixed light was 1.52–3.76 times, 1.54–3.68 times and 1.06–3.35 times of monochromatic blue light and red light, respectively.

The effect of hydrodynamics on the succession of autotrophic and heterotrophic organisms of biofilms in river ecosystems

Biofilms were cultivated for a 68-day period under different hydrodynamic conditions, and the effect of hydrodynamics on the succession of autotrophic and heterotrophic organisms of biofilms was investigated. Five obvious stages were observed during biofilm formation. At Stage I, the attachment of algae was delayed, especially under turbulent conditions. After Stage II, algal density and heterotrophic biomass of biofilms increased, which were obvious under turbulent flow. Therefore, the algal density and heterotrophic biomass of biofilms were largest under turbulent condition, followed by laminar condition, and then transitional condition. Diatoms were dominant in all flumes and were most abundant under turbulent conditions. The proportion of cyanobacteria was highest under laminar conditions. The ratio of aerobic to anaerobic bacteria decreased and their co-existence could facilitate the nitrification and denitrification in the biofilm. The ratio of monounsaturated fatty acids to saturated fatty acids was highest under turbulent conditions on the 15th day. While the ratio was highest under laminar condition on the 48th day, the high ratio indicates the high ability of biofilm to obtain nutrients, which affect the growth of algae. The regulation of hydrodynamics is a useful technology which can affect the growth of the microorganisms of biofilm, and further improve water quality.

Effects of winter conditions on Olympia oyster reproduction and larval yield

For marine invertebrates that live in temperate regions, reproductive processes are tightly linked to seasonal temperature changes, yet we know little about how reproduction will shift as winters become milder. This study examined effects of winter temperature on spring reproduction in the Olympia oyster, Ostrea lurida. Adults were exposed to two winter temperatures (7°C, 10°C) in the presence of two feeding regimes, high (50k cells/mL) and low (5k cells/mL) algal density, for either 7 weeks or 12 weeks. Following treatments, adults were induced to spawn in common conditions using hatchery techniques, and larvae were reared through settlement to assess viability. Adults overwintered in elevated temperature contained larger oocytes, and those also held in elevated algal density contained more developed sperm. Elevated temperature (10°C) under both feeding regimes resulted in larvae that tended to be larger upon release from the maternal brood chamber. However, winter temperature did not impact fecundity, larval release timing, or larval viability, nor was larval viability related to larval size upon release. In the wild, more developed gametes and larger larvae following milder winters could greatly impact recruitment patterns. When larvae are reared in the hatchery, however, elevated winter temperature will not likely impact larval viability or yield. Interestingly, overwintering duration greatly impacted broodstock survival and larval production. Regardless of winter temperature or feeding rate, broodstock overwintered in the hatchery for 12 weeks produced fewer larvae and had higher mortality during spawning compared to those held for only 7 weeks. Furthermore, broodstock overwintered in the low temperature treatment (7°C) with high algal density (50k cells/mL) experienced high mortality during spawning. Broodstock mortality is disadvantageous for hatcheries, can hinder larval production, and decrease genetic diversity of offspring. We therefore recommend that hatcheries overwinter O. lurida broodstock in slightly warmer temperatures and minimize the amount of time they are held in captivity prior to spawning. Finally, because algal density during winter treatments did not impact broodstock survival or spring larval production, hatcheries may restrict feeding without impacting production, given broodstock are in good condition upon collection.Highlights of the manuscriptMilder winters may result in more developed O. lurida sperm, larger oocytes, and larger larvae, but will not likely impact larval production timing or magnitude, indicating that O. lurida reproduction is relatively resilient to shifting winter temperatures.In a hatchery setting, O. lurida larval size upon release does not predict larval survival, and hatcheries should not presume that smaller O. lurida larvae are of poor quality.When overwintering Ostrea lurida broodstock in the hatchery prior to spring production, chilling seawater to historic winter temperatures is not necessary, nor is feeding broodstock high algal densities, and the amount of time broostock are held prior to spawning should be minimized.

Culture of Microalgae with Ultrafiltered Seawater: A Feasibility Study

The culture of microalgae is important for the production and maintenance of bivalves. One of the major challenges is to maintain the reliability of microalgae forages over the long term. The aim of this work is to use Ultrafiltered (UF) seawater to cultivate them. Thus, cultures in a volume of 300 L of 2 species of microalgae Tetraselmis and T-isochrysis, were monitored in UF water (membrane pore size: 20 nm) and in sea water usually used on the Ifremer mollusk experimental platform of Bouin (France) (Prefiltration, 3 filtrations and 2 UV). The major result is the securing of microlagae cultures with the absence of parasites in all cultures supplied with ultrafiltered water, unlike analyses of the various control cultures. In the case of T-isochrysis, 3 cultures out of 4 resulted in higher microalgae concentrations, up to 30%, in ultrafiltered water thus bringing a benefit on the algal density. These conclusions and the ease of recovering water (linked to the reduction in treatment stages) allowed a transfer of technology. In fact the 300 L cultures hitherto carried out on the experimental platform are now produced in ultrafiltered water since early 2019.