2
G.R. Carvalho et al.
First, the levels of biodiversity in our oceans are exceptional. Oceans encompass approximately 70% of the planet’s surface, and offer a diversity of habitats to
support 28 phyla of animals, 13 of which are endemic to the marine realm, compared with 11 phyla from terrestrial habitats (only one endemic, Angel 1992). High
species and phyletic diversity is commensurate with a corresponding plethora of
life-styles from floaters and swimmers, to those withstanding partial aerial exposure in intertidal zones or inhabiting deep sea hydrothermal vents at >3,500 m.
Moreover, because we know that life originated in the seas, marine taxa have been
evolving for up to 2.7 billion years longer than terrestrial counterparts. Almost all
extant phyla have marine representatives, compared to only approximately half having terrestrial representatives (Ray 1991). Importantly also, as advanced taxonomic
methods become available (Savolainen et al. 2005), and as new technologies enable
exploration of previously inaccessible habitats, many new marine species are being
discovered (e.g. Santelli et al. 2008). These include both microscopic or microbial taxa (Venter et al. 2004, Goméz et al. 2007), and also more familiar larger
organisms such as fish, crustaceans, corals and molluscs (Bouchet 2005). For example, the marine bryozoan, Celleporella hyalina, which was thought to be a single
cosmopolitan species. DNA barcoding and mating tests revealed that geographic
isolates comprised >20 numerous deep, mostly allopatric, genetic lineages (Gómez
et al. 2007; Fig. 1.1). Moreover, such lineages were reproductively isolated, yet
share very similar morphology, indicating rampant cryptic speciation. Such hidden
diversity is exemplified by recent discoveries in waters off Australia, where over
270 new species of fish, ancient corals, molluscs crustaceans and sponges new to
science were discovered among underwater mountains and canyons off Tasmania
http://www.csiro.au/science/SeamountBiodiversity.html). This is also exemplified
in marine transition zones between biogeographical provinces (e.g. between the
Lusitanian and boreal provinces, Maggs et al. 2008). All but one of the cosmopolitan diatom species investigated to date are composed of multiple cryptic species (see
review in Medlin 2007).
Second, despite the high levels of extant species diversity, marine systems
are exposed to excessive and accelerating threats from environmental change and
human activity. Threats such as pollution, over-exploitation, eutrophication, invasive species and climate change cause changes in distribution and abundance (Worm
et al. 2006), as well as localized extinctions. It is important not only to understand the mechanisms and consequences of such change to generate predictions
of response, but also importantly to enhance opportunities for recovery, resilience
and reversibility of disturbance (Palumbi et al. 2008a). Third, marine biodiversity
underpins the extent and dynamics of ecosystem functioning. Marine biota play a
key role, for example, in global nutrient recycling and climate, and provide man with
a multitude of resources and ecosystem services (products and processes provided
by the natural environment), including carbon storage, atmospheric gas regulation,
waste treatment, food provision and raw materials. Indeed, marine algae contribute
up to 40% of global photosynthesis. Globally, such marine ecosystem services have
been estimated to be valued in excess of $8.4 trillion per year for open oceanic systems and $12.6 trillion for coastal ecosystems (Costanza et al. 1997). For example,
G.R. Carvalho et al.
First, the levels of biodiversity in our oceans are exceptional. Oceans encompass approximately 70% of the planet’s surface, and offer a diversity of habitats to
support 28 phyla of animals, 13 of which are endemic to the marine realm, compared with 11 phyla from terrestrial habitats (only one endemic, Angel 1992). High
species and phyletic diversity is commensurate with a corresponding plethora of
life-styles from floaters and swimmers, to those withstanding partial aerial exposure in intertidal zones or inhabiting deep sea hydrothermal vents at >3,500 m.
Moreover, because we know that life originated in the seas, marine taxa have been
evolving for up to 2.7 billion years longer than terrestrial counterparts. Almost all
extant phyla have marine representatives, compared to only approximately half having terrestrial representatives (Ray 1991). Importantly also, as advanced taxonomic
methods become available (Savolainen et al. 2005), and as new technologies enable
exploration of previously inaccessible habitats, many new marine species are being
discovered (e.g. Santelli et al. 2008). These include both microscopic or microbial taxa (Venter et al. 2004, Goméz et al. 2007), and also more familiar larger
organisms such as fish, crustaceans, corals and molluscs (Bouchet 2005). For example, the marine bryozoan, Celleporella hyalina, which was thought to be a single
cosmopolitan species. DNA barcoding and mating tests revealed that geographic
isolates comprised >20 numerous deep, mostly allopatric, genetic lineages (Gómez
et al. 2007; Fig. 1.1). Moreover, such lineages were reproductively isolated, yet
share very similar morphology, indicating rampant cryptic speciation. Such hidden
diversity is exemplified by recent discoveries in waters off Australia, where over
270 new species of fish, ancient corals, molluscs crustaceans and sponges new to
science were discovered among underwater mountains and canyons off Tasmania
http://www.csiro.au/science/SeamountBiodiversity.html). This is also exemplified
in marine transition zones between biogeographical provinces (e.g. between the
Lusitanian and boreal provinces, Maggs et al. 2008). All but one of the cosmopolitan diatom species investigated to date are composed of multiple cryptic species (see
review in Medlin 2007).
Second, despite the high levels of extant species diversity, marine systems
are exposed to excessive and accelerating threats from environmental change and
human activity. Threats such as pollution, over-exploitation, eutrophication, invasive species and climate change cause changes in distribution and abundance (Worm
et al. 2006), as well as localized extinctions. It is important not only to understand the mechanisms and consequences of such change to generate predictions
of response, but also importantly to enhance opportunities for recovery, resilience
and reversibility of disturbance (Palumbi et al. 2008a). Third, marine biodiversity
underpins the extent and dynamics of ecosystem functioning. Marine biota play a
key role, for example, in global nutrient recycling and climate, and provide man with
a multitude of resources and ecosystem services (products and processes provided
by the natural environment), including carbon storage, atmospheric gas regulation,
waste treatment, food provision and raw materials. Indeed, marine algae contribute
up to 40% of global photosynthesis. Globally, such marine ecosystem services have
been estimated to be valued in excess of $8.4 trillion per year for open oceanic systems and $12.6 trillion for coastal ecosystems (Costanza et al. 1997). For example,