feeding pocillopora acuta with artemia nauplii

Cultivo Ex Situ de Pocillopora acuta y Técnicas Efectivas de Alimentación

Many coral reef ecosystems globally are being lost and degraded as a result of high-temperature stress driven by climate change1,2. Coral bleaching (i.e., the breakdown of the coral-algal symbiosis3) was considered relatively rare in the past4 but is now occurring more frequently5, with annual bleaching expected to occur in many regions by&#160;mid to late century6,7. This shortening of the interim period between bleaching events can limit the capacity for reef resilience8. The direct impacts of high-temperature stress on coral colonies (e.g., tissue damage9; energy depletion10) are intrinsically linked to indirect impacts at the reef-scale level, of which a reduction in reproductive/recruitment capacity is of particular concern11. This has spurred a range of applied research exploring, for example, the active in situ enhancement of recruitment (e.g., reef seeding12), new technologies for scaling-up coral restoration13, and the simulation of reproductive cues to induce reproduction in ex situ systems14. Complementary to these active interventions are the recent recognition of the advantages of heterotrophic feeding in corals under high-temperature stress15 and the exploration of the role that food provision may play in reproduction16.
Heterotrophic feeding is known to influence the performance of corals17 and has been specifically linked to increased coral growth18,19, as well as thermal resistance and resilience20,21. Yet, the benefits of heterotrophy are not ubiquitous among coral species22 and can differ based on the type of food being consumed23, as well as the level of light exposure24. In the context of coral reproduction, heterotrophic feeding has shown variable results, with observations of higher25 as well as lower26 reproductive capacity following heterotrophic feeding being reported. The influence of heterotrophic feeding on coral reproduction across a spectrum of temperatures is rarely assessed, yet in the temperate coral Cladocora caespitosa, heterotrophy was found to be more important for reproduction under lower temperature conditions27. A better understanding of the role of temperature and feeding on reproductive output is likely needed to determine whether specific reefs (e.g., reefs associated with high food availability28) possess a higher capacity for recruitment under climate change.
Similar to reproductive output, the effect of temperature and feeding on reproductive timing in corals remains relatively understudied, despite the synchronization of reproduction with abiotic/biotic conditions being an important consideration for recruitment success in a warming ocean29. Warmer temperatures have been shown to result in earlier reproduction in coral thermal conditioning studies conducted in the lab30, and this has also been observed in corals collected from natural reefs across seasons31. Yet, interestingly the opposite trend was recently observed in fed corals cultured over the course of 1 year in an ex situ flow-through system (i.e., reproduction occurred earlier in the lunar cycle at cooler winter temperatures and later in the lunar cycle at warmer summer temperatures)32. This contrasting result suggests that reproductive timing may stray from typical patterns under conditions associated with abundant energetic resources.
Long-term controlled experiments under different temperature scenarios could contribute to a better understanding of the influence of heterotrophy on reproduction in scleractinian corals. Maintaining reproducing coral colonies under ex situ conditions for multiple reproductive cycles, however, can be challenging (but see previous research32,33). Herein, straightforward and effective techniques for the active feeding (food source: Artemia nauplii) and long-term culture of a brooding coral (Pocillopora acuta) in a flow-through aquaculture system are described; yet, it should be noted that all the techniques described can also be used in recirculating aquaculture systems. To demonstrate these techniques, a preliminary comparison of the reproductive output and timing of coral colonies held at 24 &#176;C and 28 &#176;C under &#34;fed&#34; and &#34;unfed&#34; treatments was conducted. These temperatures were chosen to approximate seawater temperatures in winter and summer, respectively, in southern Taiwan30,34; a higher temperature was not chosen because the promotion of long-term ex situ culture, rather than testing coral response to thermal stress, was a primary goal of this experiment. Further, the density of Artemia nauplii before and after the feeding sessions was quantified&#160;to compare the feasibility of heterotrophic feeding at both temperature treatments.
Specifically, 24 colonies of P. acuta (mean total linear extension &#177; standard deviation: 21.3 cm &#177; 2.8 cm) were obtained from flow-through tanks at the research facilities of the National Museum of Marine Biology &#38; Aquarium, southern Taiwan. Pocillopora&#8203;&#160;acuta is a common coral species that possesses both a broadcast spawning, but&#160;typically brooding reproductive strategy35,36. The parent colonies of these corals were originally collected from the Outlet reef (21.931&#176;E, 120.745&#176;N) approximately 2 years earlier for another experiment32. Consequently, the coral colonies used in the present experiment had been reared for their entire lives under ex situ culture conditions; specifically, the colonies were exposed to ambient temperature and a 12 h:12 h light: dark cycle at 250 &#181;mol quanta m&#8722;2&#183;s&#8722;1 and were fed Artemia nauplii twice per week. We recognize that this long-term ex situ culture could have affected how the colonies responded to the treatment conditions in this experiment. We, therefore, would like to emphasize that the primary aim here is to illustrate how the described techniques can be effectively used to culture corals ex situ by demonstrating an applied example wherein the effects of temperature and feeding on coral reproduction were assessed.
Coral colonies were evenly distributed across six flow-through system culture tanks (tank interior length x width x height: 175 cm x 62 cm x 72 cm; tank light regime: 12 h:12h light:dark cycle at 250 &#181;mol quanta m&#8722;2&#183;s&#8722;1) (Figure 1A). The temperature in three of the tanks was set at 28 &#176;C, and the temperature in the other three tanks was set at 24 &#176;C; each tank had a logger that recorded the temperature every 10 min (see the Table of Materials). The temperature was independently controlled in each tank using chillers and heaters, and water circulation was maintained using flow motors (see the Table of Materials). Half of the colonies in each tank (n = 2 colonies/tank) were fed Artemia nauplii twice per week, while the other colonies were not fed. Each feeding session was 4 h in duration and was conducted in two independent temperature-specific feeding tanks. During feeding, all the colonies were moved into the feeding tanks, including the unfed colonies, to standardize the potential stress effect of moving the colonies between the tanks. The colonies in the fed and unfed treatments were positioned in their own compartment using a meshed frame within the temperature-specific feeding tanks so that only the colonies in the fed condition received food. The coral reproductive output and timing were assessed for each colony daily at 09:00 A.M. by counting the number of larvae that had been released into the larval collection containers overnight.

Autor destacado: Avance de la investigación de corales mediante la exploración de la resistencia al cambio climático, la acuicultura ex situ y las estrategias de reproducción 

Técnicas efectivas para la alimentación y el cultivo ex situ de un coral escleractiniano incubador, Pocillopora acuta

Our lab is interested in understanding climate change, resistance, and resilience in coral and exploring ex-situ aquaculture's role. Specifically, we aim to cultivate coral in a lab that can be used for restoration and research efforts. Over the past few years, we have seen major advances in coral ex-situ aquaculture, including being able to induce reproduction, as well as complete the entire coral life cycle in both broadcast spawning and brooding corals.Maintaining the long-term reproduction of brooding corals in the lab is usually quite challenging, with reproduction typically stopping after a few months. However, we found that if we culture the colonies together in mesocosm tanks and provide them with supplemental food, they can continue to produce larvae each month. In general, we have a good understanding of how feeding and temperature independently affect coral reproduction, but their interactive effects remain relatively understudied.For example, heterotrophy may have different benefits, or limitations at warmer compared to cooler temperatures. Using the protocols that we have described, we can effectively feed and culture the colonies long-term in X2 aquaculture systems, and can ultimately track the reproduction at the colony level to help infer the influence of heterotrophy on reproduction, and recruitment in a warming ocean.

Watch this Scientific Journal Video about Feeding  Pocillopora acuta with  Artemia Nauplii at JoVE.com

Feeding  Pocillopora acuta with  Artemia Nauplii  

Alimentación de Pocillopora acuta con nauplios de Artemia

Recoja dos litros de agua de mar de un tanque de alimentación independiente y viértala en un recipiente de incubación de Artemia. A continuación, conecte una bomba de aire al tubo conectado al fondo del recipiente de incubación y déjelo funcionar durante aproximadamente 10 minutos antes de agregar los quistes de Artemia. Mientras espera, mida ocho gramos de quistes de Artemia con una balanza de pesaje.Después de 10 minutos, vierta los quistes de Artemia medidos en el recipiente de incubación. A continuación, prepare el tanque de alimentación colocando el recipiente de alimentación en él, asegurándose de que la parte superior permanezca por encima de la superficie del agua. Conecte la parte exterior del tubo de la esquina del recipiente de alimentación a una bomba de aire que suministre aire a las piedras de burbujas para garantizar la circulación adecuada del agua durante la alimentación.Para enriquecer los nauplios de Artemia, agregue 1,5 mililitros de dieta de enriquecimiento al recipiente de incubación dos horas antes de la hora de alimentación deseada. Después de dos horas, cierre la válvula que suministra aire al recipiente de incubación. Después de colocar una fuente de luz en la base del contenedor de sombreado, cúbralo con una caja de cartón para excluir la luz ambiental.Deje que la luz atraiga a los nauplios de Artemia al fondo del recipiente durante cinco minutos para separar los nauplios de Artemia vivos de las conchas vacías. Después de cinco minutos, retire la caja y la fuente de luz. Coloque una jarra medidora de tres litros debajo del recipiente de incubación.Separe el tubo del recipiente de incubación, permitiendo que los nauplios de Artemia y la solución de agua de mar fluyan hacia la jarra y recojan un litro de la solución muy cerca del tanque de alimentación. Vierta los nauplios de Artemia y la solución de agua de mar a través de un colador de 100 micrómetros para separarlos del agua de mar. A continuación, enjuague los nauplios de Artemia dentro del colador dos veces con agua del tanque de alimentación.Coloque el colador en el tanque de alimentación para descargar los nauplios de Artemia. A continuación, revuelva el agua en el tanque para distribuir uniformemente los nauplios por todo el tanque. Mueva cada barra colgante con las colonias de coral adjuntas del tanque de cultivo al tanque de alimentación.Asegúrese de que la barra para colgar esté bien colocada en la parte superior del tanque de alimentación. Retire las colonias de coral después de la sesión de alimentación de cuatro horas sacando las barras colgantes del tanque de alimentación. Enjuague bien cada coral con agua de mar de los respectivos tanques de cultivo.Para eliminar los nauplios de Artemia residuales, vuelva a colocar las barras colgantes con los corales adheridos en sus respectivos tanques de cultivo.

Research

JoVE Journal

Biology

Feeding Pocillopora acuta with Artemia Nauplii

Effective Techniques for the Feeding and Ex Situ Culture of a Brooding Scleractinian Coral, Pocillopora acuta

Climate change is affecting the survival, growth, and recruitment of corals globally, with large-scale shifts in abundance and community composition ...

Investigación

Biología

Hanging Pocillopora acuta Colonies in Ex Situ Aquaculture Tanks

Colonias colgantes de Pocillopora acuta en tanques acuícolas ex situ

Quantifying Artemia Nauplii Density Pre- and Post-Feeding of Pocillopora acuta

Cuantificación de la densidad de nauplios de Artemia antes y después de la alimentación de Pocillopora acuta

Pocillopora acuta Larvae Collection and Enumeration from Culture Tank

Pocillopora acuta Recolección y enumeración de larvas en tanque de cultivo