102
Plankton in Coral-Reef Waters
coefficients vary in natural populations between 1.4 and more in a healthy,
readily multiplying phytoplankton community where the dead chlorophyllphaeophytin is practically absent, and 1 which reflects the abundance of
phaeophytin in degrading its community which, overgrazed and nutrient
depleted, is enriched with the dead detrital pigments. The results of
estimations of Fo/Fa coefficients in waters off barrier reefs around Tahiti
and Moorea Islands showed that they were the same as in the surrounding
ocean. Thus they proved that the phytoplankton grows normally in lagoonal
water rather than being only brought there with the incoming tides from the
open ocean (Table 3.14).
The above data prove that the phytoplankton in reef waters is more
abundant than in waters of the surrounding open ocean (Michel 1969;
Sournia and Ricard 1976a; Ricard 1976; Kollentz-Mishke and Fortus 1980;
Sorokin 1986b). In Fig. 3.3 a typical picture is presented of the change in
primary phytoplankton production measured on the cross sections from the
Heron Island ring reef to the open Coral Sea. At distances of 6-9 km from
the reef it decreased about 10 times, while on same kind of cross from the
lagoon of the Tarawa atoll to the open ocean it decreased by about 2 orders
at a distance of 16 km (Fig. 3.3). Within the water column of even deep
lagoons the vertical distribution of phytoplankton is usually uniform.
Sometimes phytoplankton is scarcer in the surface layer of deep lagoons
filled with waters arriving from the flat during the ebb, depleted of
planktonic algae, or with waters coming from the ocean with the tide. The
white disk transparency in reef waters in lagoons or at outer reef slopes
usually is within 10-15 m. Thus the phytoplankton photosynthesis in them is
not limited by light deficiency down to the depths of 15-25 m. A typical
curve of light attenuation in the water column of some Indooceanic reefs is
given in Fig. 3.11.
/I, f1t
Wit / kIu
o 0,25 0,5 0, 15 J
O..--.;..,...--.----i--"...,---,
'I
12
18
20L-________________ ~
Fig. 3.11. Decrease in light intensity (Wh/Wo)
in water column off the reefs of 1 Praslen I.; 2
Koetivi I.; and 3 Kargados-Karahos I.; H depth
Plankton in Coral-Reef Waters
coefficients vary in natural populations between 1.4 and more in a healthy,
readily multiplying phytoplankton community where the dead chlorophyllphaeophytin is practically absent, and 1 which reflects the abundance of
phaeophytin in degrading its community which, overgrazed and nutrient
depleted, is enriched with the dead detrital pigments. The results of
estimations of Fo/Fa coefficients in waters off barrier reefs around Tahiti
and Moorea Islands showed that they were the same as in the surrounding
ocean. Thus they proved that the phytoplankton grows normally in lagoonal
water rather than being only brought there with the incoming tides from the
open ocean (Table 3.14).
The above data prove that the phytoplankton in reef waters is more
abundant than in waters of the surrounding open ocean (Michel 1969;
Sournia and Ricard 1976a; Ricard 1976; Kollentz-Mishke and Fortus 1980;
Sorokin 1986b). In Fig. 3.3 a typical picture is presented of the change in
primary phytoplankton production measured on the cross sections from the
Heron Island ring reef to the open Coral Sea. At distances of 6-9 km from
the reef it decreased about 10 times, while on same kind of cross from the
lagoon of the Tarawa atoll to the open ocean it decreased by about 2 orders
at a distance of 16 km (Fig. 3.3). Within the water column of even deep
lagoons the vertical distribution of phytoplankton is usually uniform.
Sometimes phytoplankton is scarcer in the surface layer of deep lagoons
filled with waters arriving from the flat during the ebb, depleted of
planktonic algae, or with waters coming from the ocean with the tide. The
white disk transparency in reef waters in lagoons or at outer reef slopes
usually is within 10-15 m. Thus the phytoplankton photosynthesis in them is
not limited by light deficiency down to the depths of 15-25 m. A typical
curve of light attenuation in the water column of some Indooceanic reefs is
given in Fig. 3.11.
/I, f1t
Wit / kIu
o 0,25 0,5 0, 15 J
O..--.;..,...--.----i--"...,---,
'I
12
18
20L-________________ ~
Fig. 3.11. Decrease in light intensity (Wh/Wo)
in water column off the reefs of 1 Praslen I.; 2
Koetivi I.; and 3 Kargados-Karahos I.; H depth