and volcanic glass deposits added further evidence that the
volcano erupted at sea level after the Paleozoic, leading to
the conclusion that the volcano reached sea level early in
its growth and then later subsided to serve and the base
for future reef growth, leading to the contemporary atoll
of Enewetak. Numerous additional drillings were made
at the atoll during the latter PACE program to reinforce
and add to the earlier findings.
It is possible that coral settlement and fringing reef
growth may have begun soon after basalt islands emerged
in the Cretaceous or Eocene, lengthening the time when
corals and other reef builders first established at an earlier
age, and lengthening the process of biological evolution
thereafter. The fossil corals retrieved and identified by
John Wells from the Enewetak cores revealed 15 species
and 3 genera that no longer exist. These species may have
gone extinct or evolved into different species over time.
Likewise, 21 species of fossil foraminifera and 3 fossil
species of sea urchins are also reported from the cores.
In essence, the growth of the atoll reef over geological
time has transcended the evolution of the reef builders that
participated in its early construction.
Biogeography and ecology
Extensive marine biological surveys were accomplished
between 1947 and 1986 including dredge hauls, free diving, and hookah collections during the first decade and
transitioning to scuba diving, remote operated vehicle surveys, and submersible dives during later surveys. More
than 4,600 species of marine life have been collected and
described from Enewetak (Table 2). These include more
than 180 species of stony corals and more than 800 species
of near shore fishes reported at Enewetak Atoll. Although
the coral totals are higher than those reported at the smaller
atolls at the north end of the archipelago, they are substantially lower than the 268 species of corals now reported at
Enewetak Atoll, Marshall Islands, Table 2 Diversity levels of biota categories inventoried at Enewetak Atoll to 1987 (Compiled by
Burch in Devaney et al., 1987)
Taxa
# Species
# Genera
# Families
Sources in Devaney et al. (1987)
Algae
238
106
40
Tsuda
Fungi
112
58
18
Dunn and Reynolds
Vascular plants
123
97
48
Lamberson
Forams and non-plantonic Protozoans
279
144
58
Chave and Devaney
Porifera
40
33
26
Devaney
Actiniaria
27
21
14
Cutress and Arneson
Octocorallia
31
17
12
Devaney
Scleractinia (recent)
169
53
12
Devaney and Lang
Scleractinia (fossils)
15
10
5
Burch and Wells
Brachiopoda
4
4
4
Grant
Bryozoa
84
61
39
Cuffey and Cox
Sipuncula
77
11
3
Devaney
Echiura
2
2
2
Devaney
Platyhelminthes
31
11
10
Devaney
Nemertea
1
1
1
Devaney
Nematoda
1
1
1
Devaney
Polychaeta
132
110
34
Devaney and Bailey-Brock
Mollusca
1,240
453
151
Kay and Johnson
Insects and related
Arthropods
190
157
93
Samuelson and Nishida
Pycnogonida
5
4
4
Child
Stomatopoda
12
4
4
Reaka and Manning
Cirrepedia
10
7
6
Titgen
Lagoon plankton
285
177
82
Devaney
Ostracoda
10
10
5
Kornicker
Crustacea decapods
Devaney
Natantia
145
56
14
Devaney and Bruce
Repantia
4
3
3
Devaney
Anomura
76
29
10
Hart, Haig and Knudsen
Brachyura
293
114
16
Hart, Haig and Knudsen
Holothuroidea
20
11
5
Cutress and Rowe
Other Echinodemata
97
65
32
Devaney
Protochordates
Eldredge
Fishes
815
338
92
Randall and Randall
Reptilia
9
9
5
Lamberson
Aves
41
27
12
Berger
Mammalia
9
7
6
Reese
Miscellaneous taxa
109
77
35
Burch
Totals
4,736
2,288
902
388
ENEWETAK ATOLL, MARSHALL ISLANDS
volcano erupted at sea level after the Paleozoic, leading to
the conclusion that the volcano reached sea level early in
its growth and then later subsided to serve and the base
for future reef growth, leading to the contemporary atoll
of Enewetak. Numerous additional drillings were made
at the atoll during the latter PACE program to reinforce
and add to the earlier findings.
It is possible that coral settlement and fringing reef
growth may have begun soon after basalt islands emerged
in the Cretaceous or Eocene, lengthening the time when
corals and other reef builders first established at an earlier
age, and lengthening the process of biological evolution
thereafter. The fossil corals retrieved and identified by
John Wells from the Enewetak cores revealed 15 species
and 3 genera that no longer exist. These species may have
gone extinct or evolved into different species over time.
Likewise, 21 species of fossil foraminifera and 3 fossil
species of sea urchins are also reported from the cores.
In essence, the growth of the atoll reef over geological
time has transcended the evolution of the reef builders that
participated in its early construction.
Biogeography and ecology
Extensive marine biological surveys were accomplished
between 1947 and 1986 including dredge hauls, free diving, and hookah collections during the first decade and
transitioning to scuba diving, remote operated vehicle surveys, and submersible dives during later surveys. More
than 4,600 species of marine life have been collected and
described from Enewetak (Table 2). These include more
than 180 species of stony corals and more than 800 species
of near shore fishes reported at Enewetak Atoll. Although
the coral totals are higher than those reported at the smaller
atolls at the north end of the archipelago, they are substantially lower than the 268 species of corals now reported at
Enewetak Atoll, Marshall Islands, Table 2 Diversity levels of biota categories inventoried at Enewetak Atoll to 1987 (Compiled by
Burch in Devaney et al., 1987)
Taxa
# Species
# Genera
# Families
Sources in Devaney et al. (1987)
Algae
238
106
40
Tsuda
Fungi
112
58
18
Dunn and Reynolds
Vascular plants
123
97
48
Lamberson
Forams and non-plantonic Protozoans
279
144
58
Chave and Devaney
Porifera
40
33
26
Devaney
Actiniaria
27
21
14
Cutress and Arneson
Octocorallia
31
17
12
Devaney
Scleractinia (recent)
169
53
12
Devaney and Lang
Scleractinia (fossils)
15
10
5
Burch and Wells
Brachiopoda
4
4
4
Grant
Bryozoa
84
61
39
Cuffey and Cox
Sipuncula
77
11
3
Devaney
Echiura
2
2
2
Devaney
Platyhelminthes
31
11
10
Devaney
Nemertea
1
1
1
Devaney
Nematoda
1
1
1
Devaney
Polychaeta
132
110
34
Devaney and Bailey-Brock
Mollusca
1,240
453
151
Kay and Johnson
Insects and related
Arthropods
190
157
93
Samuelson and Nishida
Pycnogonida
5
4
4
Child
Stomatopoda
12
4
4
Reaka and Manning
Cirrepedia
10
7
6
Titgen
Lagoon plankton
285
177
82
Devaney
Ostracoda
10
10
5
Kornicker
Crustacea decapods
Devaney
Natantia
145
56
14
Devaney and Bruce
Repantia
4
3
3
Devaney
Anomura
76
29
10
Hart, Haig and Knudsen
Brachyura
293
114
16
Hart, Haig and Knudsen
Holothuroidea
20
11
5
Cutress and Rowe
Other Echinodemata
97
65
32
Devaney
Protochordates
Eldredge
Fishes
815
338
92
Randall and Randall
Reptilia
9
9
5
Lamberson
Aves
41
27
12
Berger
Mammalia
9
7
6
Reese
Miscellaneous taxa
109
77
35
Burch
Totals
4,736
2,288
902
388
ENEWETAK ATOLL, MARSHALL ISLANDS