Reinhold Leinfelder's online reef lecture

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1.3 The Importance of Reefs

1.3.1 The Importance of Reefs to Science

1.3.1.1 Ecosystem research, evolution

just some figures and facts:

most complex ecosystem, highest diversity at phylum and class-level. Vertrebrates especially diverse.

highest diverse marine ecosystem at species level

Numbers from modern reefs:

500.000 to more than 1 Million species assumed

ca. 60.000 species known

ca. 5000 species of fishes

more than 3.800 species of corals from which ca. 1300 species (of 246 genera) are scleractinian stone corals

4000 species of mollusks only from the Great Barrier Reef, Australia

25% of all oceanic species are from reef settings.

Some figures for comparison:

Tab 1: Exampes for species numbers (after Consortium Systematics Agenda 2000, Veron 1995 and others):

	known species	estimated species number
viruses	5.000	ca. 500.000
bacteria	4.000	400.000 – 3 millions
funghi	70.000	1 – 1.5 millions
protista	40.000	100.000 – 200.000
algae	40.000	200.000 – 10 millions
plants	250.000	300.000 – 500.000
vertebrates	45.000	50.000
round worms	15.000	500.000 – 1 million
mollusks	70.000	200.000
crustaceans	40.000	150.000
chelicerata	75.000	750.000 – 1 million
insects	950.000	8 – 100 millions
reef organisms (all groups)	60.000	> 1 million

all known genera of scleractinian corals (Triassic to modern): ca. 1800
all known genera of tabulate / rugose corals (paleozoic): ca. 280 (Tabulata) + 800 (Rugosa), + some other groups

Known stone corals (genera/species):
pacific (from W to E): Galapagos: 5 / 17; Great Barrier Reef 70 / 300; Indonesian Archipelago 70 / 450, Maldives 50 / 200, Persian Gulf 30/50, Red Sea 50 / 200.
Atlantic: Caribbean 20/50; Brasil 7 / 10?

Red: modern tropical coral reef domains.
green: coral diversities (genera/species)

Map from Wells & Hanna 1992, Data largely from Veron (1995)

see also biogeographic maps in Veron 1995

Fig. 1.1: Presentation of animal species scaled to their biomass. Insects dominate by far. Small square up represents about 1000 known species. Coelenterates, including the reef corals do not have a high proportion. Nevertheless, biodiversity of marine systems is highest in coral reefs. From consortium Systematic Agenda 2000, slightly modified.

All species: ca 10 - several hundred millions ???, known about 1.5 millions.
Rain forest insects: at least 1 million speecies
About 3 species die out every hour, about 27.000 die out every year.

More superlatives (just some examples):

Cnidocil-expulsion (the stinging, lasso-type fibre of certain coelenterats) speeds up at 400.000 metres/sec²(which is 6000 times more than a rocket; a gun bulled reaches 500.0000 metres/sec²).
We will see that reefs represent a gigantic macroorganism which phantastic symbioses and life communities. We will also see that reefs are a perfect monitor for equilibrium conditions and environmental change.
Another, most fascinating story is the optimizing aspect of reef evolution which now lets them thrive in superoligotrophic settings, which we may also call the nutrient deserts of the oceans.
Reefs exist since about 3.5 millions of years, more widespread since 2.5 millions of years;
Coral reefs exist since about 500 million of years;
Modern scleractinian corals exist since about 240 Mio a (million of years);
since 190 Mio a (late Lower Jurassic) many coral groups are similar to today's
since about 100 Mio a (around boundary between lower and upper Cretaceous) modern coral-coralline algae reefs exist
since about 20 Mio a (Miocene): coral reefs conquered highest energy, high-abrasive (hurricane-influenced) settings (algal ridge development), causing strong separation (compartmentalization) of open ocean waters and lagoons.
(more about this in the Reef Evolution Section)

This page is part of www.palaeo.de/edu/reefcourse, last changes 28/1/03 by R. Leinfelder