CH07: Past Marine Ecosystem Changes

FIGURE 7.1 Four-million-year-old Antarctic shift. A crinoid, typical of current Antarctic marine communities. The circumpolar current formed around Antarctica 4 million years ago, resulting in major ecosystem changes. Sharks and bony fishes were lost, resulting in proliferation of crinoids and ophiuroids (brittle stars). Source: Photo courtesy of Jeff Jeffords.

FIGURE 7. 2 Electron micrograph of foraminifera tests FIGURE 7.2 Electron micrograph of foraminifera tests. Source: Pearson et al. (2001). Reproduced with permission from Nature.

FIGURE 7.3 Marine range changes. At the Last Glacial Maximum (LGM), 12 species were found together along the Southern California coast that now are now nearly absent from the area. This plot shows the present southern and northern range limits (points) of species that were co-occurring in the shaded area at the LGM. Source: Roy et al. (2001).

FIGURE 7.4 Current coastline superimposed on coastline at LGM and coastline with Greenland/Antarctica melted for Northern Europe (a and d), Florida (b and e) and Southeast Asia (c and f). Source: Courtesy of William F. Haxby, Lamont-Doherty Earth Observatory of Columbia University.

FIGURE 7.5 Depth of mixing for CO2 in Atlantic, Pacific, and Indian Oceans. The three color panels (a-c) indicate depth of mixing along the transects mapped in the insets. a) Atlantic; b) Pacific and c) Western Indian Ocean. CO2 from human emissions mixes into surface waters more rapidly than deep waters. CO2 is poorly mixed in bottom waters in all three oceans, but is highest in North Atlantic waters, where it is carried downward in thermohaline circulation. Source: Sabine et al. (2004).

FIGURE 7.6 Sea surface temperature response to El Niño. Normal conditions (top) and El Niño conditions (bottom). In El Niño conditions, warm water pools more widely in the tropical Pacific and water temperatures are higher in the eastern tropical Pacific, blocking upwelling along South America and in the Galapagos. Source: Courtesy of Mark Bush. From Ecology of a Changing Planet, 3rd edition. Benjamin Cummings.

FIGURE 7.7 Calcite-secreting organisms a) Coccolithophore; b) tridacnid clam; c) manila clam (Venerupis philippinarum). Source: From Wikimedia Commons.

FIGURE 7.8 Aragonite-secreting organisms Scleractinian corals (a-b) and a pteropod (Limacina helicina). Coral reefs of aragonite provide structure which is the base of many tropical marine foodwebs. Pteropods are important food sources for salmon, mackeral and cod.. Source: Courtesy U.S. National Oceanic and Atmospheric Administration (NOAA).

FIGURE 7.9 Coral photosynthesis response to temperature and salinity. Temperature and salinity exert strong controls over growth and distribution of species. In this example, the photosynthetic response of corals to both temperature and salinity are shown. Source: Roessig et al. (2004). With kind permission from Springer Business Media.

FIGURE 7.10 Reef builders and reef gaps. Reef builders have varied over the past 500 million years. Dominant reef builders have only been modern scleractinian corals for the past 50 million years. Prior dominant reef builders included stony sponges, calcareous algae, bryozoans and other types of corals (rugose, tabulate). Some of these reef builders, such as calcareous algae are important (but not dominant) in building modern reefs. Others, such as rugose corals have become extinct, opening the way for the emergence of scleractinian corals 220 million years ago. The major coral extinctions often coincide with ‘reef gaps’, five periods in which there is no evidence of major reef building anywhere in the world. The reef gaps are times for which there is no fossil record of reefs—no fossil reef has ever been dated to these periods. In contrast, ‘mega-reef’ periods have left extensive fossil reef deposits in many parts of the planet. As discussed in Chapter 9, the reef gaps correspond to major extinction episodes in other species. Source: Stanley and Fautin (2001).