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

Summary

Climate change is impacting coral reef ecosystems globally. Corals sourced from ex situ aquaculture systems can help support restoration and research efforts. Herein, feeding and coral culture techniques that can be used to promote the long-term maintenance of brooding scleractinian corals ex situ are outlined.

Abstract

Climate change is affecting the survival, growth, and recruitment of corals globally, with large-scale shifts in abundance and community composition expected in reef ecosystems over the next several decades. Recognition of this reef degradation has prompted a range of novel research- and restoration-based active interventions. Ex situ aquaculture can play a supporting role through the establishment of robust coral culture protocols (e.g., to improve health and reproduction in long-term experiments) and through the provision of a consistent broodstock supply (e.g., for use in restoration projects). Here, simple techniques for the feeding and ex situ culture of brooding scleractinian corals are outlined using the common and well-studied coral, Pocillopora acuta, as an example. To demonstrate this approach, coral colonies were exposed to different temperatures (24 °C vs. 28 °C) and feeding treatments (fed vs. unfed) and the reproductive output and timing, as well as the feasibility of feeding Artemia nauplii to corals at both temperatures, was compared. Reproductive output showed high variation across colonies, with differing trends observed between the temperature treatments; at 24 °C, fed colonies produced more larvae than unfed colonies, but the opposite was found in colonies cultured at 28 °C. All colonies reproduced before the full moon, and differences in reproductive timing were only found between unfed colonies in the 28 °C treatment and fed colonies in the 24 °C treatment (mean lunar day of reproduction ± standard deviation: 6.5 ± 2.5 and 11.1 ± 2.6, respectively). The coral colonies fed efficiently on Artemia nauplii at both treatment temperatures. These proposed feeding and culture techniques focus on the reduction of coral stress and the promotion of reproductive longevity in a cost-effective and customizable manner, with versatile applicability in both flow-through and recirculating aquaculture systems.

Introduction

Many coral reef ecosystems globally are being lost and degraded as a result of high-temperature stress driven by climate change^1,2. 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 mid to late century^6,7. This shortening of the interim period between bleaching events can limit the capacity for reef resilience

Protocol

1. Hanging coral colonies in ex situ aquaculture tanks

1. Position a notched bar (length x width x height: 75 cm x 1 cm x 3 cm), hereafter referred to as a "hanging bar", across the culture tank in preparation for hanging the coral colonies.
   NOTE: The hanging bar used in this experiment was custom-made, but a simple PVC pipe with protruding screws (i.e., to act as the notches) would be sufficient as long as it can be positioned in a stable manner across the top of th.......

Discussion

This preliminary assessment of the effect of temperature and feeding on coral reproduction revealed differences in reproductive output and timing among colonies cultured under distinct treatment conditions. Further, it was found that feeding Artemia nauplii to coral colonies appeared to be effective at relatively cool (24°C) as well as warm temperatures (28 °C). These combined findings highlight the applicability of these straightforward techniques for the feeding and culture of reproducing scleractini.......

Materials

Name	Company	Catalog Number	Comments
Artemia cysts	Supreme plus	NA	Food source
Chiller	Resun	CL650	To cool down water temperature if needed
Conductivity portable meter	WTW	Cond 3110	To measure salinity
Enrichment diets	Omega	NA	Used in Artemia cultivation
Fishing line	Super	Nylon monofilament	To hang the coral colonies
Flow motors	Maxspect	GP03	To create water flow
Heater 350 W	ISTA	NA	Heaters used in tanks
HOBO pendant temperature logger	Onset Computer	UA-002-08	To record water temperature
LED lights	Mean Well	FTS: HLG-185H-36B	NA
Light portable meter	LI-COR	LI-250A	Device used with light sensor to measure light intensity in PAR
Light sensor	LI-COR	LI-193SA	NA
Plankton net 100 µm mesh size	Omega	NA	To collect larvae and artemia
Primary pump 6000 L/H	Mr. Aqua	BP6000	To draw water from tanks into chiller
Propeller-type current meter	KENEK	GR20	Device used with propeller-type detector to measure flow rate
Propeller-type detector	KENEK	GR3T-2-20N	NA
Stereo microscope	Zeiss	Stemi 2000-C	To count the number of artemia
Temperature controller 1000 W	Rep Park	O-RP-SDP-1	To set and maintain water temperature