Ocean Acidification A National Strategy to Meet the Challenges of a Changing Ocean (2010) / Chapter Skim
Currently Skimming:
4 Effects of Ocean Acidification on Marine Ecosystems
4 Effects of Ocean Acidification on Marine Ecosystems
Pages 59-82
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 59... ...
. While it is important to understand how ocean acidification will change ocean chemistry and the physiology of marine organisms, as reviewed in chapters 2 and 3, what is equally critical is to understand how these effects may scale up to popula tions, communities, and entire marine ecosystems.
|
From page 60... ...
These groups produce the bulk of the calcium carbonate that make up the reef structures, which in turn support the high biodiversity of coral reef ecosystems. Recent analyses illustrate that 1There are two types of calcifying macroalgae that are important to reef formation in tropical coral reef ecosystems: crustose coralline red algae (coralline algae)
|
From page 61... ...
; Tropical coral reef and fish (photo courtesy of Susan Roberts, NRC) ; Coccolitho uneditable bitmapped images phores (photo courtesy of Mitch Covington, BugWare Inc.)
|
From page 62... ...
Acidification may decrease reef growth by reducing calcification rates, reproduction, and recruitment. It may also increase the dissolution or erosion of existing reef structures.
|
From page 63... ...
. Similar to tropical reef corals, calcification rates of reefbuilding crustose coralline algae are affected more strongly by ocean acidification at elevated temperature (Anthony et al., 2008)
|
From page 64... ...
The overall calcium carbonate budget and reefbuilding capacity of a reef depend not only on carbonate production rates, but also on dissolution rates and carbonate removal rates due to erosion and sediment transport. Acidification has been shown to increase dissolution rates of coral reefs; in one extreme example, the skeletons of corals placed in seawater with pH of 7.37.6 dissolved completely (Fine and Tchernov, 2007)
|
From page 65... ...
4.2 OPEN OCEAN PLANKTONIC ECOSySTEMS The open ocean is not a uniform ecosystem; the components vary greatly by location. In open ocean systems, microscopic photosynthetic organisms -- phytoplankton -- which grow in the sunlit surface waters, serve as the base of diverse and complex food webs including zooplankton and larger freeswimming animals such as fish and marine mammals.
|
From page 66... ...
Reduced rates of calcification, along with the shoaling of the satura tion horizons for calcium carbonate minerals to shallower depths will also affect the marine calcium carbonate cycle (see Chapter 2) through decreased CaCO3 burial in sediments, additional carbon storage from increased production of extracellular organic carbon by phytoplankton (see below)
|
From page 67... ...
, which may also affect nutrient availability for phytoplankton in surface waters. Ocean acidification has the potential to alter the marine nitrogen cycle which controls much of primary production in the sea.
|
From page 68... ...
In this way, changes in the microbial community composition and activity triggered by ocean acidi fication may act as a feedback on climate change. 4.3 COASTAL ECOSySTEMS Coastal ocean ecosystems include a variety of benthic habitat types, including seagrass beds, kelp forests, tidal wetlands, mangroves, and others.
|
From page 69... ...
Impacts on many other species not yet studied are likely. Indirectly, acidification may affect the productivity and composition of some coastal ecosystems by affecting the key species at the base of coastal food webs.
|
From page 70... ...
They are also subject to a diversity of stresses caused by human activities, such as organic matter and nutrient inputs, pollution by toxic organic compounds and metals, acid rain, sea level rise and other climate change effects, and overfishing. The effects of ocean acidification on coastal ecosystems may be small relative to the effects of these natural and humaninduced stresses.
|
From page 71... ...
The ambient flora and fauna, par ticularly benthic organisms, may well be affected by annual exposure to acidic and, in some cases, corrosive hypoxic water. Depending on the differential tolerances of organisms to changes imposed by acidification, there are likely to be shifts in community com position or productivity of the various ecosystems.
|
From page 72... ...
For example, populations with indi viduals possessing genetic variations that tolerate the expected changes in ocean chemistry may result in higher survival or reproductive success because of morerapidthanexpected adaptation to the new conditions. It is not known whether coastal ecosystems that do not currently experience natural hypoxic and low pH events are less susceptible to incremental shifts in regional ocean chemistry due to ocean acidification.
|
From page 73... ...
A unique habitat type in the deep sea that deserves particular atten tion is coldwater coral communities. Coldwater corals, also known as deepwater or deepsea corals, form ecosystems that are in some ways the deepwater counterparts of tropical coral reefs.
|
From page 74... ...
It must be noted that this is the only study on the response of a coldwater coral species to ocean acidification. Deepsea coral communities are also abundant and ecologically sig nificant on thousands of seamounts throughout the world ocean that could be affected by ocean acidification.
|
From page 75... ...
Considering the expected rapid shoaling of the calcite and aragonite saturation horizons with future ocean acidification and the observed relationship between coral distributions and existing saturation hori zons, deepsea coral communities on seamounts or bioherms are likely to be impacted.
|
From page 76... ...
, calcium carbonate export to the ocean interior will be reduced, which would in turn decrease the potential of foraminiferal tests to act as ballast in the transport of organic carbon to the deep sea (Schiebel, 2002; Moy et al., 2009)
|
From page 77... ...
. Calcifying macroalgae and marine invertebrates, including coldwater corals, sea urchins, and mol luscs, make up significant components of the rich benthic communities in high latitudes, and these are thought to be at risk with increasing ocean acidification.
|
From page 78... ...
4.6 LESSONS FROM THE gEOLOgIC PAST Evidence from the geologic record indicates that the Earth previ ously experienced periods of high atmospheric CO2 which also changed ocean chemistry. Studies of past ocean chemistry and coincident changes in marine ecosystems may provide insight into the potential impacts of ocean acidification today and in the future.
|
From page 79... ...
Nonetheless, a number of factors limit the utility of the PETM as an analog for the detailed effects of acidification on the biota and carbon cycle of the ocean. First, the amount of carbon released is not well constrained because the exact source is unknown, and the magnitude of carbon isotope excursions in different carbon isotopic records vary by roughly a factor or two, with larger excur sions typically found in soil carbon records than in deep sea sediments.
|
From page 80... ...
As a consequence, responses of marine ecosystems to the ongoing increase in CO2 may not be analogous to the changes in biological diversity associated with events in the deep past. Further development of proxy measurements, such as the use of boron isotopes to estimate ocean pH changes, could provide additional information on the rate and extent of changes in ocean CO2 and pH during these past climatic events.
|
From page 81... ...
, lakes (Carpenter et al., 1999) , coral reefs (Norström et al., 2009)
|
From page 82... ...
to ocean acidification will be difficult. In coral reefs, for example, whether the loss of corals is due to rising temperature or from ocean acidification may have little relevance in the overall impact on the ecosystem (loss of corals impacts the base function of the ecosystem)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.