Goodbye Caribbean Coral

[b-dog]

Here is an article about how the algae on the coral reefs is winning the fight. The Caribbean corals are doing much worse than the corals in the Indo-pacific and in the article it says that it might be because there are less fish that eat coral. Here is the article:
Caribbean reefs less resilient › News in Science (ABC Science)
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I agree with this because when people try to maintain coral in an aquarium algae is one of the biggest problems and almost all of the fish that are good at eating algae are from the Indo-pacific. The Foxface rabbitfish is a machine at eating algae and the Kole Tang has special teeth for scraping algae while the yellow and sailfin tangs are excellent algae eaters as well. The Naso tang is the only fish that will eat Lobophora algae. The blue tang from the Caribbean/Atlantic is not too useful for this however.

Here is a video about what fish help to keep coral growing in an aquarium all of which live in the Indo-pacific region.

[/FONT]Reef Fish Selection - YouTube
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The Indo-pacific is very lucky to have so many different species...
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[skearse]

I'll add my two cents here...speaking mostly from aquarium experience; not sure exactly how valid some of that experience 'scales up' to the real thing, but anyway:

Algae growth in an aquarium is symptomatic of other issues-high nutrient (nitrogen and phosphorous in particular) loadings in particular. Macro-algaes will certainly out-compete coral/zooxanthellae algae growth where N&P loadings are 'high'. Aquarists can (and many do) overload tanks (in this case, tank meaning a 210-gallon glass box rather than an Al80, lol) with clean-up crews, herbivores, etc. rather than address the root issue, which is poor water quality. Alternatively, a lot of reefers (myself included) use refugium type systems specifically designed to grow macro-algae in order to help keep display (reef) tank conditions pristine. There are some other Atlantic fish species that do fairly good job of algae maintenance (angels come to mind), but, again, those are corrective type actions rather than preventive. I would suggest that alot of the root cause lies in the conditions that create an environment that allows macro-algaes to preferentially thrive and over-run reefs. And, for what it's worth, I think alot of that could probably be traced to the actions of humans-not trying to turn this into a 'man bad/save Gaea' type thing but...I'd venture to guess that the Caribbean reefs and eco-systems see a lot more two-legged traffic (not just divers; all tourists) and would not be surprised to see historical studies that suggest that the Caribbean reefs 'downturn' tracked closely with increases in tourism to the same ecosystems.

 

[Wookie]

I didn't read the article, so I don't know where the authors are smpling, but in remote places away from habitation (Navassa, Dry Tortugas, Flower Gardens, Mona) the corals are healthier and more vibrant than I've seen since 2005. The staghorn and elkhorn are growing at prodigious rates and the colors in the reef building corals (boulder corals) look fantastic. I expect a warm year this year, maybe not a mass bleaching, but perhaps mild bleaching, but I am happy to see the overall health of the reefs has improved dramatically, at least where I go diving. Now, the places that dump their sewage on the reef, treated and untreated, have a terrible decline in reef health. The correlation is pretty obvious, nutrients bring algae, algae smothers coral. When the FKNMS passed their no sewage discharge ban a couple of years ago, the boaters howled. Now, however, the song is a little different with the corals coming back. There is a downside, however. Turns out that raw sewage helps turtle grass beds. The turtle grass beds off of Key Largo are really hurting now. I'd rather have coral reef than turtle grass, however.

 

[b-dog]

I'll add my two cents here...speaking mostly from aquarium experience; not sure exactly how valid some of that experience 'scales up' to the real thing, but anyway:

Algae growth in an aquarium is symptomatic of other issues-high nutrient (nitrogen and phosphorous in particular) loadings in particular. Macro-algaes will certainly out-compete coral/zooxanthellae algae growth where N&P loadings are 'high'. Aquarists can (and many do) overload tanks (in this case, tank meaning a 210-gallon glass box rather than an Al80, lol) with clean-up crews, herbivores, etc. rather than address the root issue, which is poor water quality. Alternatively, a lot of reefers (myself included) use refugium type systems specifically designed to grow macro-algae in order to help keep display (reef) tank conditions pristine. There are some other Atlantic fish species that do fairly good job of algae maintenance (angels come to mind), but, again, those are corrective type actions rather than preventive. I would suggest that alot of the root cause lies in the conditions that create an environment that allows macro-algaes to preferentially thrive and over-run reefs. And, for what it's worth, I think alot of that could probably be traced to the actions of humans-not trying to turn this into a 'man bad/save Gaea' type thing but...I'd venture to guess that the Caribbean reefs and eco-systems see a lot more two-legged traffic (not just divers; all tourists) and would not be surprised to see historical studies that suggest that the Caribbean reefs 'downturn' tracked closely with increases in tourism to the same ecosystems.

Sure, pollution and siltation are the major cause of reef destruction. Many of the resort areas just dump raw pollution into the ocean and this adds a nutrient overload and causes the algae to overgrow the reefs. I don't know how this is going to stop however as the more tourists that come the more pollution that is released into the ocean. But these same conditions exist in the Indo-pacific but I think that because of the amount of clean-up crews and herbivorous fish there it is able to overcome the algae overgrowth. Hopefully, there will be ways to reduce the pollution entering the ocean so that algae overgrowth is not dependent upon clean-up crews and herbivorous fish.

 

[EastTNDiver]

My son and I did a Blackbeard's trip three years ago. On the east side of the Exuma Sound, towards the southern end of Eleuthera, the algae was pretty abundant.

 

[Hank49]

There is someone on here from the Bahamas who is theorizing that lionfish may be actually benefitting the reefs there by indirectly depleting the algae and bringing back the coral. I don't remember all the details but he showed before LF and after LF photos. Interesting.

 

[Jeff Godfrey]

At least for deeper reefs the litureature indicates otherwise.

M.P. Lesser and M. Slattery, 2011. Phase shift to algal dominated communities at mesophotic depths associated with lionfish (Pterois volitans) invasion on a Bahamian coral reef. Biol Invasions 13:1855–1868.

Abstract
Mesophotic coral reefs (30–150 m) have been assumed to be physically and biologically connected to their shallow-water counterparts, and thus may serve as refugia for important taxonomic groups such as corals, sponges, and fish. The recent invasion of the Indo–Pacific lionfish (Pterois volitans) onto shallow reefs of the Caribbean and
Bahamas has had significant, negative, effects on shallow coral reef fish populations. In the Bahamas, lionfish have extended their habitat range into mesophotic depths down to 91 m where they have reduced the diversity of several important fish guilds, including herbivores. A phase shift to an algal dominated ([50% benthic cover) community occurred simultaneously with the loss of herbivores to a depth of 61 m and caused a significant decline in corals and sponges at mesophotic depths. The effects of this invasive lionfish on mesophotic coral reefs and the subsequent changes in benthic community structure could not be explained by coral bleaching, overfishing, hurricanes, or disease independently or in combination. The significant ecological effects of the lionfish invasion into mesophotic depths of coral reefs casts doubt on whether these communities have the resilience to recover themselves or contribute to the recovery of their shallow water counterparts as refugia for key coral reef taxa.

 

[b-dog]

Scuba diving through mounds of algae could be sort of interesting if you think about it. Maybe one day fish like the surgeon fish and rabbitfish in the Indo-pacific will evolve in the Caribbean that will eat the algae too. It will be interesting to see what happens in the Caribbean from an evolutionary standpoint.

 

[Guba]

To Hank49
The fellow to which you are referring is Fred Riger, of Grand Bahama Scuba. However, his hypothesis is a little more complex. What he says he has observed over the past two decades was a gradual increase in small reef fish that predate upon certain crustaceans and sea urchins. When these "cleaner" organism numbers fell, he noticed thick mats of algae form that decreased the overall health of the corals themselves. He surmised that the big increase in the first level predators (the reef fish) was due to falling numbers of mid-level predators (cod, grouper, and snapper), which were being extensively hunted and fished out of that area.
Enter the lionfish...since lionfish are mid-level predators, the number of reef fish decreased. The cleaner crustaceans and urchins rebounded, and the algae was greatly reduced and even controlled. Note that he has no true empirical data and no formal studies to back his observations. All he has is twenty years of observing the areas in which he dives on a nearly daily basis, but he does record his observations fairly closely, including photographic means. It's an elegant hypothesis and, in my opinion, could warrant closer scrutiny. I was so intrigued that I actually went to Grand Bahamas to meet and dive with him and discuss his observations.

As for Lesser and Slattery's paper, it's very well done and impressive, and it sheds a lot of light on the skewing of predator/prey loads as algal, cleaner, and predator numbers shift. What I did not see, however, was any mention of the multi-tier predator relationships, particularly involving non-fish "cleaners" (the crustaceans and urchins Fred Riger mentions). All I saw were the references and stats involving fish herbivores, and those were experimentally sampled in non-benthic environments, although I admit I need to re-read the paper to give it a closer scrutiny.

All of this does point out a very encouraging point...studies are now being conducted. Fred has a hypothesis, but little documented data. What I would like to see are some independent research entities take up specific hypothetical parameters within the lionfish invasion field for closer scrutiny. In my opinion, we need to look at these ideas much more closely, because if removal of mid-level predators from an area has the type of impact suspected, it means a lot MORE than "what to do about the lionfish?". It means we have to totally re-think our policies for removing predator species from coral environments and possibly how to take steps to increase their numbers naturally.

 

[Doc]

I have no data, no hypothesis.

I do have 45 years of Caribbean diving to reflect upon.

It has gotten worse every year, never better.

In 1970, Cayman and the Bahamas were spectacular (underwater).

When the land gets disturbed by development, it's all over- siltation and run-off.