Marine Reserves Necessary, Diving Hol Chan

School of grunts

School of grunts

Green moray eel

Green moray eel

Group underwater shot

Group underwater shot

Our last day dive was at Hol Chan Marine Reserve. We returned to where we first started. After practicing our diving techniques for the past two weeks, we were all way more confident than the first. The first day, the 11 of us were broken up into two groups: the newly certified and the advanced . No one was allowed to take cameras until everyone displayed their ability to dive. I was part of the newly certified group, since I had just got my open water certification the weekend before the trip. My group only ventured around the sea grass beds in the shallows, trying to avoid the channel. It was wicked cool to see all the fish and turtles swimming around, but didn’t get the full effect of the marine reserve until the last day. Before breaking off into the same groups, we all had a photo shoot. This time our cameras were allowed. I have a subscription to Dive Magazine. Within it, they post people with their magazines in exotic locations. I thought that we should get a group shot underwater to try and get our picture posted. I enjoyed the small groups a lot, because when the 11 of us are in the water together checking out the same area it tends to get claustrophobic. Constantly bumping into people is annoying, never mind getting a fin in the face. After separating and heading out, we swam through the sea grass beds and got to the channel, you were greeted by large schools of fish and a wall of corals. The walls were filled with all kinds of fish and inverts living within. The fish swam around like they knew they would not be fished there. They ranged from small to large. Marine reserves prove to be the best area to encounter the greatest percentage of marine life. There was a great deal of green moray eels, and their heads where the only things really seen during the day. Some corals had their polyps displayed, while others were not out yet. The coral polyps would be out for our night dive later on (I must add watching the corals feed on the blood worms from our flashlights was pretty sweet). There weren’t too many gorgonians, and the corals did not have too much algae cover. There really needs to be more marine reserves in the world. It is upsetting to know less than 1% of the ocean is actually protected. Reserves can help fish grow larger, stay healthier and reach greater abundance and diversity. This was definitely proven true swimming at all the different dives sites located around San Pedro. Coral sites absolutely covered in algae had little signs of inverts and far few fish. Many were small in proportion. Sometimes it takes some hands on experience to really learn and this trip was incredible to partake and learn from. The sustainability of the ocean, marine life and coral reef is necessary and all need to be aware.

Comparing Invertebrate Counts

The invertebrate creatures that life on the coral reefs are in integral part of the vast and complicated ecosystem that has been referred to as the rainforest of the oceans. There is much about these ecosystems that we do not understand, and compiled with the complicated effects of human impact reefs makes it even more difficult to understand. However, after compiling years of data and the results inferred, it has been determined that there are key indicator species that can be used to determine the health of a reef. Almost as one would do with a canary in a mine shaft.

The species that have been determined by Reef Check to be indicator organisms based on economic (harvested for the aquarium trade) and ecological (balancing the algal growth) value are;
1) Banded coral shrimp (Stenopus hispidus)
2) Diadema urchins
3) Pencil urchin (Eucidras spp.)
4) Collector urchin/sea egg (Tripneustes sp.)
5) Triton (Charonia variegta)
6) Flamingo tongue (Cyphoma gibbosum)
7) Georgonian (sea fan, sea whip)
8) Lobster (Palinuridea)

While in our reef ecology class we reviewed and studied an article that studied and almost certainly concluded that the diadema (black spine) urchin was not only integral, but perhaps the most important, or key stone, invertebrate species within the coral reef ecosystem. Following a mass die out of diadema (aprox 95%) in 1984, the increase of alga was almost instantaneous. However, since the return of the diadema in recent years (since the mid 90s) they greatly reduced microalgal (from >60% to <5%) which in turn increased coral growth. The study was conducted throughout the Caribbean, but the discovery of the impact of the diadema was a place called Dairy Bull, in Jamaica. It was here that there as actually been an increase in coral cover in the past two decades (in vast contrary to the rest of the Caribbean), almost 100% more living coral and 90% less algal cover then it did in 1995. This coral growth is occurring even while overfishing is still a problem. This phase shift in coral growth  appears to always be preceded by the recovering and increased population of the diadema urchin.
Source:
http://www.int-res.com/articles/meps_oa/m403p091.pdf

On the first dive located at, Buena Vista, we discovered invertebrate species in the low single digits only. This had also been a trend in most of the dive sites we had been to prior to our Reef Check dives. In addition to the lack of invertebrates, their was large amounts of coral disease and bleaching. Their was a large amount of algal proliferation, as well as a great over abundance of georgonians. The site just looked sick.

In contrary, the second dive site, Coral gardens, looked radically healthier. The amount of diadima urchins was around 50 and pencil urchins was even more then that. Also, reef urchins, which are not counted by Reef Check would have easily surpassed 200 if they had been counted. There were more flamingo tongues, and even two collector urchins, the georgonian count was also much lower. The coral substrate itself was vastly more abundant and disease and bleaching was far less prevalent. Also, there was significantly less algal proliferation. Both sites are legally allowed to be fished and the species discovered at each site were about even.

With out conducting a purely scientific study we can not make any fact based conclusions. However, from the data we gathered and what we were able to see just from being there supports the findings of the article we studied in class and the study it was based on. The diadema urchins, and other herbivores are indeed a keystone species. They are integral to the promotion of of healthy coral and increased coral growth. In addition to this, what we observed at another site, Hol Chan, also supports the article. While not a Reef Check site (so we did not study, just notice and observe), it is protected from fishing, which means far greater number of fish species. However the overall health of the site was less the that of Coral Gardens, and in parallel to that the amount of diadema we noticed was far less.

The coral reefs are an incredibly complex biosphere, and the more we study the more we learn. Reef Check, and the observations we make while conducting it, is an invaluable asset into this learning process. Just seeing that the two locations we studied were so different and the species we found in each site is an enormous help. The fact that what we found supports conclusions by other scientific data is large step forward in the understanding of healthy reefs. Hopefully, with time , the damage that has been done to the reefs can be stopped and the health of these underwater biosphere can be returned to their natural unparalleled state of beauty.

 

 

Invasive Lionfish

I was very curious to talk to someone about lionfish, since I know it is an invasive species in the Atlantic and they are quite overpopulated. Diving the past week and a half, I have been very surprised to not see that many. On day 2, a lionfish was spotted on an artificial reef off the end of a dock. He wasn’t very big. A couple days later Jimmy was snorkeling off the end of Ecologic Divers’ dock before a dive and spotted 2 little lionfish hovering at the bottom. He let a couple of the workers know and they jumped in and speared the fish. It wasn’t until diving out in the Great Blue Hole and the dive sites nearby that I encountered some very large lionfish. A total of three were counted lingering around the reef waiting for prey to swim by and be eaten up. There were many fish at Lighthouse Reef, due to it being a marine reserve, so the lionfish were living like kings, overindulging on the other fish. A final lionfish was discovered on the night dive we did at Hol Chan Marine Reserve yesterday. Wondering why there weren’t many spotted, I decided to talk with a local. I was informed that the reason why I was not finding any lionfish on the dives outside the reef was because they like to hang out within. They choose to do so because that is where all the smaller fish hang out; smaller fish are easier prey. They are also primarily located on the south side of the island, not a place where we have really been diving. The locals try to curb the population by spearing them whenever possible. This is a reason why barracudas tend to swim by your side: they are waiting for their fish handout, like your pet dog follows you for a treat. Nearby restaurants specialize in lionfish cuisine. I have yet to try it, but want to venture out to get some before our departure. Ultimately, the overpopulated lionfish has not yet taken over the reefs along San Pedro. Hopefully predators will catch on from the handouts and start feeding on the lionfish themselves.

Jimmy and a speared lionfish.

Jimmy and a speared lionfish.

Lionfish at lighthouse reef.

Lionfish at lighthouse reef.

Barracuda swimming alongside.

Barracuda swimming alongside.

Nightswimming deserves a quiet night.

People often talk of nostalgia, of the good times where an unexpected event was shared between a group of people. Tonight, our band of merry scientists have something to bond over for the rest of our lives. Not only was it the last dive of the trip but also it was something that was truly unique, a night dive. We had been pushing for one all trip and finally we got an opportunity. Our entire time down here, the weather had not agreed with us. Today though, it was our chance and we could not have asked for a better night to dive. We had a fairly calm current going out. Although we had to kick a little bit harder on the way out, our return was nice and easy with no effort at all. Along the way, we saw lobsters, sting rays, parrot fish, snappers, and many other aquatic life. I personally saw a lion fish. The sighting of the night was by Dr. John. He saw a moray eel having a little late night snack on a parrot fish. It was a really cool experience at about three quarters of the way into the dive. We stopped at a sandy spot, gathered round together and turned off our flashlights. Slowly we waved our hands in the air and the bio-luminescence turned on like tiny black lights all around us. It was something to be seen. Although not everyone enjoyed the dive as much as the group(its pretty scary in the dark ocean at night), everyone can say that it was an experience that they’ll never forget.