Day 112 , 1 December 2017 — Reef monitoring at North Male Atoll

The Marine Lab team has been preoccupied this past month with reef monitoring surveys at a total of ten sites. This includes the two islands Angsana Ihuru and Vabbinfaru as well as with nearby sites like Coral Garden. It’s been simultaneously tiring and rewarding, and my brain now automatically classifies whatever I see underwater. Whatever I can’t classify or identify with confidence when we’re in the water, I end up having a strong compulsion to take a picture of. This will most probably end up being stored in a folder on my computer, labelled “ID later”, that I may or may not ever get to look through. I guess you could say that it’s an occupational hazard after all.

These are some of the photos of us hard at work at the start of the reef monitoring surveys when we took a boat out to nearby local reefs at Coral Garden, and on the East of Barros. When Steve and I went down at one of the sites there was a pretty strong current we had to swim against as we lay the transects…that’s my workout for the month! I’m really grateful now for the chance to have worked on the reef surveys in Malapascua with Reef Alert and the Thresher Shark Research Conservation Program because there would be no freaking way I’d be able to maintain trim in a stationary position, writing, with a current pushing me down the transect (Medel, if you ever read this, you have trained us well).

 

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Me doing the benthic survey and recording down the coral growth form. Also, this picture is particularly special because it was my 100th dive! What a great way to reach a hundred by doing reef monitoring!

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I swear Steve lays the nicest transects. They are always so nice and straight and I don’t know if he does it on purpose or not, but he somehow manages to get it with the cm side up instead of the inch side up and that makes everything so much easier!?

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Zim holding the benthic cheat sheet and smiling in between our dives at the different points of each island.

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And that’s Danielle! Armed with all her transect tapes, buckled down and ready to go.

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And Steve again! Cause that was a really productive dive!

 

We do the reef monitoring surveys in a team. The first person (usually Steve, Danielle or Charlie) lays out the transect tape to estimate the size and abundance of key functional groups of fish (E.g. Algal grazers like surgeonfish, corallivores like butterflyfish). The second person (usually me or Zim) starts recording the benthic cover at intervals over the 20m-long transect. Finally, we take pictures using a quadrat at intervals along the entire transect so we can later analyse the pictures for coral recruits and to estimate the amount of available substrate corals can colonise onto.

 

The fish surveys sound hard in theory, but I assure you they’re even harder in real life. Imagine a school of fish like these blue striped snappers in front of Charlie, and having to estimate how many there are in a matter of seconds before they swim away. Now in addition to counting how many there are, you also have to estimate a size range. And in addition to that, you need to know what kind of fish you’re looking at. And of course since you’re diving, you also have to pay attention to your buoyancy so you’re not fumbling around like a potato underwater. THAT IS SOME HIGH LEVEL MULTITASKING I’LL TELL YOU.

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Schools of fish such as these blue striped snapper (Lutjanus kasmira) are particularly tough to estimate.

For reef monitoring, it’s lucky the fish we count are restricted to key functional groups. Groupers and snappers act as a proxy for food-fishing pressure, angelfish as a proxy for aquaria-fishing pressure, parrotfish and surgeonfish as a proxy for the amount of grazing that takes place on the reef and butterflyfish….well, cause they eat corals and it’s a sign of reef health. It’s about to be way more challenging once I start collecting data for my research and we have to identify the fish down to a species level. I’m keeping my fingers crossed that I somehow manage to figure that out, but that’s a whole other story for next time.

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Groupers such as this white lined grouper (Anyperodon leucogrammicus) act as a proxy for fishing pressure

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Emperor angelfish (Pomacanthus imperator) act as a proxy for fishing in the aquarium trade. This one was found munching on bits of algae.

 

Benthic cover is basically a fancy way for saying stuff that’s on the bottom of the sea floor. The idea is to monitor how the substrate changes over time. For instance, the reefs before the bleaching event were occupied primarily by the branching or plating types of staghorn coral (Acropora sp.), but now, it seems as though these areas are now occupied by dead corals encrusted with a thin film of turf algae. Also, more hardy types of coral such as the boulder coral (Porites sp.) seem to persist more readily in this post-bleaching environment.

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A large boulder Porites coral doing exceptionally well despite the bleaching event.

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Meanwhile, lots of branching and finger type corals like this cauliflower coral (Pocillopora sp.) don’t seem to do as well. This particular coral is partially bleached.

 

After the bleaching events, algae encrusts the coral, and over time, this coral breaks down into rubble or acts as new substrate for new coral recruits to colonise onto.IMG_0028

Thin films of turf and calcareous algae encrusting the surfaces of dead corals

Even while the corals are dead, they act as refuge for marine life. The complex structure of these branching corals are often home to juvenile fish such as the lunar wrasses (Thalassoma lunare), the blue lined wrasse (Stethojulis albovittata), the brown tang (Zebrasoma scopas) and a whole range of pygmy gobies as well.

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An incredibly tiny green pygmy goby (Eviota albolineata), that’s barely a centimetre long, perched on top of dead coral.

 

It sounds sad that corals have been destroyed by the bleaching events, but we learnt loads more about corals from Dr. Peter Mumby and Dr. Chris Doropoulos this week. Both of them are visiting scientists from the Marine Spatial Ecology Laboratory, from the University of Queensland, and have been supervising Tania’s PHD work on coral rubble. Pete recounted the bleaching event in 1998 when 25% of the colonies he was observing were almost entirely dead. Yet, it amazed him that small existing patches of coral that survive were able to completely regenerate the reef. “In pristine environments, corals can bounce back and defy our expectations,” he said on an optimistic note. That’s why it is imperative to make sure that there are as little stressors on the reef as possible while it recovers. That means that fishing activities are controlled, particularly for algivores that play an important role in keeping algae growth under control so they don’t outcompete new coral recruits. It also means that coral predators need to be kept under control to, so we need to be consistent in the removal of crown-of-thorns starfish from our reefs. Just the other day, Charlie and I found a crown-of-thorns under the jetty happily liquifying a new Acropora recruit. (We picked it up with a coconut husk and that crown-of-thorns is no more)

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A small encrusting Galaxea coral emerging from all the rubble

“In pristine environments, corals can bounce back and defy our expectations” –Dr. Peter Mumby

Something new I learnt from Chris is that when bleaching events occur, it’s usually the small coral recruits (aka coral babies) that aren’t as affected by the bleaching. These corals, as well as other small patches of coral that survive the bleaching events, can repopulate the reef if they are within the right conditions. For one thing, the reef cannot be overgrown with algae. Pete explained that this phenomenon is similar to what you’d find in a garden…Too many weeds and your plants won’t grow well. You need to keep de-weeding your garden. If you have a healthy fish population in your reefs, these fish will graze on the algae, preventing them from overgrowing the reef. In reefs that have been overharvested or overfished, this ecological chain is disrupted, and severely affects the recovery of the reefs.

It’s been so much fun having everyone around, and I’m sad to have to seen some of them go off slowly one by one!

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That’s all of us (except Aru, the birthday boy who was off celebrating)! From left to right, Ali, me, Steve, Zim, Pete, Tania, Chris, Charlie and Danielle! (Thanks Steve for the photo!)

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We’ve got a pretty big team now! From left to right, that’s Steve, Aru, Zim, Tania, Charlie, Danielle, me and Esther, squinting in the blinding sun.

It’s been a busy month so far, and I also got stung by some plankton pretty badly on my cheeks and sadly missed out on the last few days of reef monitoring. I now look like I’ve contoured my face really badly but some new skin is growing over so yay I can’t wait to get back into the water soon.