In 1997 two participants of the Reef Check 1997, Dr. Verena Lubini
and Heinrich Vicentini, visited Angaga island and checked the reef condition
in six locations. In order to determine possible changes in the reef and
variations when different people apply the same methods, we checked the
same sites in 1998 again. The coordinates of the different locations were
determined in 1997 by the GPS. Although we had no GPS at hand, we could
relocate the different sites easily because of a good site description
as well as the valuable directions of Jochen Gommers.
In the following sections we give a brief description of each reef check
site. This includes the geographic location, possible human impact, the
exposure to surf and waves as well as the weather conditions during the
check. Moreover, we outline our observations concering coral bleaching,
fish and invertebrate species as well as other important observations.
This location was the first transect we checked and we were surprised by the poor condition of the reef. More than 80% of the hard corals were dead and covered by a thin layer of a grey-brown algae. 5%-10% were still alive and approximately the same fraction was partially or completely bleached.
Of the target species we observed mainly butterfly fishes (Chaetodon
sp.) and one species of sea cucumber (Bohadschia graeftei).
| Date | Time | Depth | Visibility | Sea & air temperatures | Description |
|---|---|---|---|---|---|
| June 29, 1998 | 10:15 am | 10 m | 20 m | 30 °C, 29 °C | Some clouds, slight waves |
| June 29, 1998 | 3:30 pm | 3 m | 15 m | 30 °C, 29 °C | Rainy & cloudy, calm |
The collected transect data is available as MS Excel spreadsheets:
On this transect, we faced a very similar picture: Most corals were dead (>85%) and covered by algae. The majority of the remaining corals were severly bleached. Leather corals (Sarcophyton sp.) seemed to be less affected by bleaching. In both depths, we observed mostly butterflyfish (Chaetodon sp.), few sweetlips (Plectorhinchus sp.) and two medium groupers (Cephalopholis sp.). Of the target invertebrates, we observed mainly sea cucumbers. The main species found was Bohadschia graeftei.
Even at night, almost no living corals could be detected. However, on
this night dive we were able to observe five banded coral shrimps (Stenopus
hispidus), two diadema (Diadema sp.) and five pencil (Heterocentrotus
sp.) urchins, three crown of thorns (Acanthaster planci) as
well as 20-30 lobsters (Palinurus sp.). Besides, we observed a small
group of sepia (Sepia prashadi), two turtles (Caretta caretta)
and one white tipped reef shark (Triaenodon obesus).
| Date | Time | Depth | Visibility | Sea & air temperatures | Description |
|---|---|---|---|---|---|
| June 30, 1998 | 10:00 am | 10 m | 20 m | 30 °C, 30 °C | Some clouds, calm |
| June 30, 1998 | 3:00 pm | 3 m | 12 m | 30 °C, 30 °C | dito |
The collected transect data is available as MS Excel spreadsheets:
In accordance to the previous transects, less than 10% of the corals were still alive. Around 5% were affected by coral bleaching and a large fraction of the dead corals (Acropora sp.) were covered by algae. In several locations we observed rides in the reef caused by broken and tumbling table corals (Acropora hyacinthus). Due to the natural exposition of this part of the reef the damages are considered to be caused by storm and erosion.
On the transect we observed mostly butterfly fish (Chaetodon sp.),
some groupers (Cephalopholis sp.) and few sweetlips (Plectorhinchus
sp.). In three meters depth we frequently observed the sea cucumber
Bohadschia
graeftei and we observed on both transects few edible sea cucumbers
and giant clams (Tridacna gigas).
| Date | Time | Depth | Visibility | Sea & air temperatures | Description |
|---|---|---|---|---|---|
| July 2, 1998 | 3:45 pm | 10 m | 15 m | 27 °C, 30 °C | Monsoon, stormy & rain, rough sea |
| July 3, 1998 | 3:40 pm | 3 m | 12 m | 29 °C, 30 °C | Cloudy & windy, waves & current |
The collected transect data is available as MS Excel spreadsheets:
As on Angaga, around 90% of the corals were dead and mostly covered
by a thin layer of algae, indicating their rather recent death. 5% of the
corals were at least partially bleached and only 5% seemed healthy. Except
for some butterfly fish, we observed almost none of the target species.
On both transects we counted only two groupers (Cephalopholis sp.),
three giant clams (Tridacna gigas) whereas on Angaga only few specimens
of the sea cucumber Bohadschia graeftei were observed.
| Date | Time | Depth | Visibility | Sea & air temperatures | Description |
|---|---|---|---|---|---|
| July 4 1998 | 10:30 am | 10 m | 15 m | 29 °C, 30 °C | Sunny, some clouds, calm, slight waves |
| July 5 1998 | 3:40 pm | 3 m | 15 m | 29 °C, 30 °C | Sunny, calm |
The collected transect data is available as MS Excel spreadsheets:
Since the tila did not reach depths as shallow as three meters, we did the transect on five meters. As an overall impression we considered the reef to be more colorful and in a better state than the previous places. Nevertheless, most hard corals were dead and mostly covered by algae, 80% in 10m and 90% in 5m depth. It seems that the bleaching process in greater depths was delayed such that in 5m depth 5% whereas in 10m depth still 15% of the corals were at least partially affected by coral bleaching.
In contrast to our first impression, we observed a fair amount of butterfly
fish (Chaetodon sp.), but just one sweetlip (Plectorhinchus sp.)
as well as few edible sea cucumbers and few Bohadschia graeftei
together with one crown of thorns (Acanthaster planci). On the transects
we observed many anemonefish (Amphiprion sp.). Many specimens were
not in the vicinity of an anemona and many anemonas were occupied by more
than two couples of clown fish. This indicates that many anemonas have
recently died.
| Date | Time | Depth | Visibility | Sea & air temperatures | Description |
|---|---|---|---|---|---|
| July 3 1998 | 9:45 am | 10 m | 12 m | 29 °C, 30 °C | Cloudy, windy, slight waves |
| July 6 1998 | 3:30 pm | 5 m | 20 m | 30 °C, 30 °C | Sunny, hot, calm |
The collected transect data is available as MS Excel spreadsheets:
The transect in ten meters depth was located in a reef wall. 80% of the corals were dead and about 15% partially bleached. Apart from the ususal numbers of butterfly fish (Chaetodon sp.) we observed only one grouper (Cephalopholis sp.), one giant clam (Tridacna gigas) and two sea cucumbers (Bohadschia graeftei). The structure of the reef wall must have been very beautiful when the corals were still alive.
In three meters depth the state of the reef was desastrous: It must
have been a nice plateau covered with table corals but during the Reef
Check it looked like craters on the moon, dead and deserted! More than
90% of the corals were dead and covered by a thick layer of algae. The
rest was at least partially bleached. Apart from a couple of butterfly
fishes (Chaetodon sp.) we observed hardly any other species, not
even sea cucumbers.
| Date | Time | Depth | Visibility | Sea & air temperatures | Description |
|---|---|---|---|---|---|
| July 8 1998 | 2:45 pm | 10 m | 15 m | 31 °C, 30 °C | Sunny, calm |
| July 8 1998 | 4:00 pm | 3-4 m | 20 m | 31 °C, 30 °C | dito |
The collected transect data is available as MS Excel spreadsheets: