Monitoring and Maintaining Corals Post-transplantation Copy

Previously, we stated there was little value in closely monitoring coral growth rates in the nurseries. However, when it comes to transplanting corals, it is vitally important that you have a practical and on-going monitoring program.

It is straightforward for most anybody to fill coral nurseries and show high survival and growth rates, as long as they are well planned and well maintained. Most programs fail during the transplantation stage or in the long-term survival of the transplanted corals.

According to the coral restoration database created in 2020, most projects achieved survival rates of 70% or greater in the nursery stages after one year. However, most did not report or monitor the survival of corals post-transplantation, and none for more than 24 months. This has led to some projects being considered ‘successful’ which did not achieve their goals of increasing the breeding population of corals on the reef or improving reef resilience.

A lack of long-term monitoring and reporting has led to wasted time and resources as other projects follow the same path – unaware that they are also repeating the same mistakes.

Transplanted corals should be monitored long-term for:

  • Survival
  • Diversity
  • Disease and compromised health
  • Growth and reproductive ability (optional)

In the following sections, we will go into more detail on the practical ways to monitor each parameter and its importance.

Survival of transplants

Corals grown on the nursery or large fragments of opportunity transplanted directly to the restoration site on artificial reefs or the natural substrates must be tracked.
They should all be more or less healthy when transplanted, so the cause of any mortality should be investigated. In most cases, a sample population of the transplanted corals should be tagged. The size of this population will differ depending on the project size and the resources available, but it should be between 5-20% of the total number of corals transplanted.

Permanent transect lines and quadrants may also be utilized, depending on the program’s preferences and the monitoring study’s requirements. Rapid survival and mortality data on each subsequent survey should be collected on all tagged corals. If mortality rates increase significantly from one week to the next, more detailed surveys should be implemented to identify the threat.

Generally, with new transplants, the most significant threats are dislodging and predation. Stressed corals release specific amino acids which corallivores can detect in the water. Corallivores are then attracted to and preferentially feed on those stressed corals.

It is vital to be careful when out-planting corals to minimize abrasions during transportation or change in depth/light levels at the final placement site.

Volunteers should also be on the lookout for coral predators in the area and relocate or remove them. If the abundance of beneficial organisms such as sea urchins is low and fouling organisms such as macroalgae are an issue, volunteers can also move more into the transplantation site.

The first few days post-transplantation are the most vital in terms of maintenance. One primary consideration is to rescue corals that were not secured well or displaced. Over time, less frequent maintenance is required. As the reef establishes itself, then, ideally, no ongoing maintenance will be needed.
Monitoring will still need to go on, ideally for several years.

Monitoring provides you with an understanding of the long-term implications of your work as your reefs undergo multiple chronic and acute stress events such as bleaching, storms, and disease outbreaks.

Through careful monitoring, you will understand which colonies are doing well and should be encouraged and which may not warrant too much devotion of your project’s time and energy. You will start better comprehending your region’s various unique ecosystem dynamics.

It is successful if your restoration project shows high relative long-term survival rates compared to natural areas. If you experience mass mortality of your restored reefs following these events, you may need to pay more attention to the diversity of genres and genotypes you are utilizing.

Monitoring Growth

For academic and scientific studies, monitoring coral growth rates can be important. However, this is less important for local managers trying to conserve or restore large areas of reefs.

There may be instances when this is worth the time and resources required and can be accomplished much like in the nursery stage. Tagged corals can be directly measured or mapped, and photographed over time.

For all projects, photographs are a great way to show your progress to the community or your students and volunteers.

The most important aspect of achieving useful photographs is to recreate them as perfectly as possible. You should develop a system of photographing the corals and artificial reef structures that is easy to replicate each time.

One of the more straightforward ways to do this is to set rules for photographs from the beginning using the tools and equipment you always have with you, such as a compass.

For example, each structure or plot of transplants can be photographed from all aspects (North, East, South, and West). Photographs can be taken from a distance at which the structure or plot fills the camera’s viewing window, from a height of about 1 meter.

Your criteria may differ, but the main objective is to set rules that work for you, that you can remember, and that you replicate on each dive to the area without relying on memory.

A similar system should be established for individually tagged corals, ensuring the tag is included in the photo to ease organization and post-processing back on land. When taking initial photographs, remember to plan the shot to apply when the coral is larger.

Sometimes, it may be warranted or desired to set up photo point markers for restoration areas or individual structures of corals. This can be done by pounding a metal stake into the sand or a nail into a dead coral head onto which the camera will be set for each subsequent photo. This is more important if your program wants to show coral growth time-lapses to raise awareness or educate non-divers about your activities.

In most photos, it is also helpful to include a reference of known size to establish scale, often a ruler or 1m PVC pipe.

For direct measurements, the coral should be measured on two planes to give the continuous living tissue’s maximum diameter and height. In most cases, counting the number of branches is not necessary nor practical.

Monitoring Diversity

In all but the most extreme cases (i.e., Acropora in the Caribbean), your project should be taking an ecosystem approach and restoring for increased diversity of corals. This means a wide variety of genera, species, and genotypes.

Regular surveys of your restoration site using the techniques described in the EMP manual for quadrants and transects will allow you to monitor the diversity of the genera and species of corals in your restoration site. This should either match or be increased from your reference sites.

If coral diversity is less in your restoration site than in your reference site, you may need to adjust your techniques and focus on collecting naturally produced fragments of rare corals over the abundant ones. It can also help to switch a focus from naturally produced fragments to unsecured coral recruits (juvenile corals recruited to pieces of rubble).

Include in your dive briefing a few words on which corals you already have a high abundance of and deter your volunteers or assistants from focusing on those species.
To achieve high rates of genotypic diversity, you need to think in the long term and gather corals from a large reef area. This means that weekly collection dives should be completed in slightly different areas of the reefs to increase the genetic variation of the feedstocks in the nurseries and the resultant restoration areas.

Other ways to ensure high genetic diversity include:

  • Avoid corals through asexual propagation, which leads to reduced genetic variability and can cause genetic bottlenecking, inbreeding/outbreeding depressions, or reproductive failure.
  • Encourage reproduction on the reef by ensuring reproductive-sized colonies are not isolated but have conspecifics nearby.
  • When feasible, create feedstocks of corals by culturing larvae covered in our Coral Spawning and Larval Culturing Course.

Monitoring for disease and compromised health

You must monitor transplants for predation, disease, overgrowth, and other signs of compromised health and take action to prevent mass mortality. This may mean focusing on predator removals, having nurseries for other species, such as giant clams or sea urchins, or focusing on corals species that can successfully grow on the reef in changing conditions rather than on historically present species.

The EMP manual introduced you to the methods for tracking coral health, diseases, and bleaching. These will not change for your restoration site. It is essential to plan, have reference sites similar to your restoration areas, and ensure that you have the manpower and resources for at least several years of monitoring, ideally a decade or more.

We also recommend you have a copy of Conservation Diver’s Coral Disease Identification and Monitoring Manual.

Reproductive Ability

Reproductive failure can mean the local extinction of reefs and is a vital concept to plan for throughout the restoration process.

Reproductive failure can occur in various ways, but at the most fundamental, it occurs when there are not enough reproductively viable adults, they are too sparse or isolated, or they are monospecific. When transplanting corals, try to maintain breeding populations by planting similar species near each other but not creating monospecific stands.

This is another reason why we never produce corals through asexual reproduction and try to collect coral fragments over large spatial and temporal scales. It may also ensure that there is ample availability of clean substrate for coral recruitment through the removal of macroalgae or the placement of artificial substrates.

It is essential to monitor the reproductive ability of reefs by performing occasional size class and fragment/recruitment surveys (about 2-3 times per year). This is also important when planning your restoration activities, as often, areas with high recruitment rates do not require intervention, as they will be able to recover on their own over time. Conversely, those recruitment-limited reefs may be targets for biological restoration as they may need more active assistance to continue producing successive generations that can adapt to changing climates and other disturbances.

Reporting Monitoring Data

Ideally, every scientifically based reef restoration project would report its findings to a peer-reviewed scientific journal. However, in practice, this can be more difficult, especially with local reef managers who may not be affiliated with a University, be proficient in English, or have the time to devote to the paper writing and publication process.
Despite those barriers, it is still very important to track your corals’ health, your project’s success, and the lessons learned. One way to do this is with so-called ‘grey literature,’ or properly formatted reports that are not necessarily peer-reviewed and may be published on your website.

If you are a member of Conservation Diver, we have set up a program through which you can send your reports to us, and we will compile them, publish them on our website, and pass those on to other researchers.

You should also reach out to other researchers, NGO’s, and groups in your region to see about sharing your data or collaborating. Lastly, you might also look for international databases such as the one by Mermaid.