Marine chemical ecology: chemical signals and cues structure marine populations, communities, and ecosystems.
TL;DR: How chemical cues regulate critical aspects of the behavior of marine organisms from bacteria to phytoplankton to benthic invertebrates and water column fishes is reviewed.
Abstract: Chemical cues constitute much of the language of life in the sea. Our understanding of biotic interactions and their effects on marine ecosystems will advance more rapidly if this language is studied and understood. Here, I review how chemical cues regulate critical aspects of the behavior of marine organisms from bacteria to phytoplankton to benthic invertebrates and water column fishes. These chemically mediated interactions strongly affect population structure, community organization, and ecosystem function. Chemical cues determine foraging strategies, feeding choices, commensal associations, selection of mates and habitats, competitive interactions, and transfer of energy and nutrients within and among ecosystems. In numerous cases, the indirect effects of chemical signals on behavior have as much or more effect on community structure and function as the direct effects of consumers and pathogens. Chemical cues are critical for understanding marine systems, but their omnipresence and impact are inadequ...
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TL;DR: The potential for marine organisms to adapt to increasing CO2 and broader implications for ocean ecosystems are not well known; both are high priorities for future research as mentioned in this paper, and both are only imperfect analogs to current conditions.
Abstract: Rising atmospheric carbon dioxide (CO2), primarily from human fossil fuel combustion, reduces ocean pH and causes wholesale shifts in seawater carbonate chemistry. The process of ocean acidification is well documented in field data, and the rate will accelerate over this century unless future CO2 emissions are curbed dramatically. Acidification alters seawater chemical speciation and biogeochemical cycles of many elements and compounds. One well-known effect is the lowering of calcium carbonate saturation states, which impacts shell-forming marine organisms from plankton to benthic molluscs, echinoderms, and corals. Many calcifying species exhibit reduced calcification and growth rates in laboratory experiments under high-CO2 conditions. Ocean acidification also causes an increase in carbon fixation rates in some photosynthetic organisms (both calcifying and noncalcifying). The potential for marine organisms to adapt to increasing CO2 and broader implications for ocean ecosystems are not well known; both are high priorities for future research. Although ocean pH has varied in the geological past, paleo-events may be only imperfect analogs to current conditions.
2,995 citations
TL;DR: Evidence from direct and indirect approaches using geochemical and genetic techniques suggests that populations range from fully open to fully closed and a full understanding of population connectivity has important applications for management and conservation.
Abstract: Connectivity, or the exchange of individuals among marine populations, is a central topic in marine ecology. For most benthic marine species with complex life cycles, this exchange occurs primarily during the pelagic larval stage. The small size of larvae coupled with the vast and complex fluid environment they occupy hamper our ability to quantify dispersal and connectivity. Evidence from direct and indirect approaches using geochemical and genetic techniques suggests that populations range from fully open to fully closed. Understanding the biophysical processes that contribute to observed dispersal patterns requires integrated interdisciplinary approaches that incorporate high-resolution biophysical modeling and empirical data. Further, differential postsettlement survival of larvae may add complexity to measurements of connectivity. The degree to which populations self recruit or receive subsidy from other populations has consequences for a number of fundamental ecological processes that affect population regulation and persistence. Finally, a full understanding of population connectivity has important applications for management and conservation.
1,640 citations
TL;DR: It is concluded that the best way to protect salt marshes and the services they provide is through the integrated approach of ecosystem-based management.
Abstract: Salt marshes are among the most abundant, fertile, and accessible coastal habitats on earth, and they provide more ecosystem services to coastal populations than any other environment. Since the Middle Ages, humans have manipulated salt marshes at a grand scale, altering species composition, distribution, and ecosystem function. Here, we review historic and contemporary human activities in marsh ecosystems—exploitation of plant products; conversion to farmland, salt works, and urban land; introduction of non-native species; alteration of coastal hydrology; and metal and nutrient pollution. Unexpectedly, diverse types of impacts can have a similar consequence, turning salt marsh food webs upside down, dramatically increasing top down control. Of the various impacts, invasive species, runaway consumer effects, and sea level rise represent the greatest threats to salt marsh ecosystems. We conclude that the best way to protect salt marshes and the services they provide is through the integrated approach of ecosystem-based management.
770 citations
TL;DR: It is shown how the use of global variables of environmental forcing that have recently become available and gas exchange relationships that incorporate the main forcing factors will lead to improved estimates of global and regional air-sea gas fluxes based on better fundamental physical, chemical, and biological foundations.
Abstract: The past decade has seen a substantial amount of research on air-sea gas exchange and its environmental controls. These studies have significantly advanced the understanding of processes that control gas transfer, led to higher quality field measurements, and improved estimates of the flux of climate-relevant gases between the ocean and atmosphere. This review discusses the fundamental principles of air-sea gas transfer and recent developments in gas transfer theory, parameterizations, and measurement techniques in the context of the exchange of carbon dioxide. However, much of this discussion is applicable to any sparingly soluble, non-reactive gas. We show how the use of global variables of environmental forcing that have recently become available and gas exchange relationships that incorporate the main forcing factors will lead to improved estimates of global and regional air-sea gas fluxes based on better fundamental physical, chemical, and biological foundations.
626 citations
TL;DR: The results imply that humans could be substantially impacting iron and bioavailable iron deposition to ocean regions, but there are large uncertainties in the authors' understanding.
562 citations
References
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TL;DR: It is demonstrated that blue crabs reduce foraging activity in the presence of odors released from freshly injured conspecifics, which should facilitate survival by distancing unharmed individuals from areas of intense conflict.
Abstract: The selective advantage of avoiding lethal predation typically outweighs the benefits of obtaining food. Many aquatic organisms reduce their foraging activity after detecting the presence of injured conspecifics, but responses of cannibalistic animals are less obvious because injury-related cues might attract rather than deter alerted consumers. We investigated the effect of injured con- specifics on the foraging responses of blue crabs Callinectes sapidus, which are ecologically impor- tant consumers known for their aggressive behavior and cannibalistic tendencies. In estuarine tidal channels, we presented natural foragers with a choice between baited control traps and baited treat- ment traps that included an additional odor source. Traps containing an injured blue crab captured significantly fewer blue crabs than paired control traps deployed for periods of up to 18 h. Injured blue crabs that were aged prior to trap deployment confirmed that deterrent cues related to the injury had dissipated within 22 h. Traps containing chemical solutions derived from injured blue crabs elicited avoidance by conspecifics, but neither uninjured blue crabs nor injured stone crabs Menippe mercenaria were deterrent. Together these data demonstrate that blue crabs reduce foraging activ- ity in the presence of odors released from freshly injured conspecifics. Not only should such avoid- ance responses facilitate survival by distancing unharmed individuals from areas of intense conflict, but the associated changes in blue crab foraging behavior could also have broader ecological conse- quences through impacts on other trophic levels.
53 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...…baited with fish, fish plus an undamaged blue crab, fish plus a newly damaged blue crab (to mimic predation), or fish plus a newly damaged stone crab (to mimic predation on a co-occurring crab), blue crabs avoid traps with the damaged blue crab relative to the other bait types (Ferner et al. 2005)....
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...…commonly investigated in the laboratory, sometimes in flumes, and occasionally in the field (Fishelson 1997, Finelli et al. 2000, Weissburg et al. 2002, Ferner et al. 2005, Burkepile et al. 2006), but the specific compounds that cue search behavior and movement to a source are rarely investigated....
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TL;DR: This work compared the effects of chemical cues from host algae on different life history stages of the ''arboreal'' sea urchin Holopneustes purpurascens and identified the first known example of chemically mediated ontogenetic shifts in host plant use in a marine herbivore.
Abstract: Habitat selection that maximizes both larval settlement success and subse- quent juvenile and adult performance is a fundamental challenge for marine benthic or- ganisms with complex life histories (e.g., planktonic larvae). For benthic herbivores, chem- ical cues from macroalgae can strongly influence both larval settlement/metamorphosis and subsequent performance. We compared the effects of chemical cues from host algae on different life history stages of the ''arboreal'' sea urchin Holopneustes purpurascens .I n sublittoral habitats near Sydney, Australia, H. purpurascensoccurred primarily on two algal hosts: red alga (Delisea pulchra) and kelp (Ecklonia radiata). Urchins on E. radiata were significantly larger than those on D. pulchra, but no recruits occurred on E. radiata .I n experiments, larvae rapidly metamorphosed in the presence of D. pulchra, but metamor- phosis was delayed or nonexistent in the presence of E. radiata. D. pulchra produces a polar chemical inducer of metamorphosis not found in E. radiata. In contrast to larval metamorphosis, feeding and performance of juvenile and adult urchins were considerably worse on D. pulchra than on E. radiata. Feeding experiments confirmed that nonpolar metabolites (halogenated furanones) in D. pulchra deter feeding. Adding natural concen- trations of the most abundant furanone to otherwise palatable diets completely inhibited feeding. Urchins fed D. pulchra had reduced survival, growth, and reproduction compared to those fed E. radiata. H. purpurascens did not thrive on the alga on which they prefer- entially settled; therefore, postrecruitment movement from D. pulchra to E. radiata was crucial to fitness. Urchins in D. pulchra beds moved between plants at night and preferred E. radiata in habitat preference experiments. Movement was constrained by diurnal pred- ators, particularly damselfish Parma microlepis. When H. purpurascenswas removed from their algal hosts during the day (but not at night), P. microlepis ''clipped'' their spines and tube feet. Removal of 10% of an urchin's spines and tube feet was fatal. H. purpurascens recruits onto a host that does not support persistence of the benthic phase and then shifts host plants, incurring a predation risk. Though chemically mediated, ontogenetic shifts in host plant use are known for insect herbivores, this is the first known example in a marine herbivore.
51 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...…on the chemically defended red alga Delisea pulchra; polar metabolites from this alga induce urchin metamorphosis, but the sea urchin cannot survive on the alga long-term owing to the seaweed’s production of nonpolar halogenated furanones that strongly deter urchin feeding (Williamson et al. 2004)....
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...A deeper appreciation for these chemical mechanisms will further our fundamental understanding of the ecological processes that structure marine systems, their relative importance in selecting for present day traits, and how these processes combine to determine the structure of marine communities....
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TL;DR: Changes in herbivore behaviour and plant chemistry provide evidence that brown algae and higher plants utilize similar salivate-based signals in the induction of defence against herbivory, and the possibility that such responses could be either highly conserved or a convergent strategy is discussed.
Abstract: Summary
1
It is well understood that herbivory can cause plants to elevate production of defensive chemicals in their tissues. One of the key questions in understanding patterns of potential coevolutionary links between plant and herbivore is ‘what switches these induced plant defences on?’ Until cues are identified, understanding the evolutionary and ecological significance of defences in the context of the plant is difficult.
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We induced host plant resistance in a marine macroalga (Ascophyllum nodosum) in the absence of herbivory by application of α-amylase, known to exist in mollusc saliva. There was a demonstrable change in the behaviour of a subsequent herbivore (Littorina obtusata) consistent with herbivore induction, i.e. reduced consumption, more but smaller meals and greater movement. We also produced a concomitant increase in the level of phlorotannins, compounds associated with defence against herbivory.
3
Such changes in herbivore behaviour and plant chemistry provide evidence that brown algae and higher plants utilize similar salivate-based signals in the induction of defence against herbivory. Thus the possibility that such responses could be either highly conserved or a convergent strategy is discussed.
51 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...Although the source of this cue was not investigated in this study, later work by Coleman et al. (2007) found that Ascophyllum could be induced by an enzyme from snail salava....
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...The brown seaweed studied by Coleman et al. (2007) is known to induce increased phlorotannin-based chemical defenses when attacked by gastropods that are deterred by these compounds, but not when attacked by an isopod 204 Hay A nn u....
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...…herbivores that generally live on the plants they consume; Hay et al. (1987)] feeding and movement among hosts over scales of centimeters and meters (Coleman et al. 2007), but also appear to affect foraging by some sea birds over landscapes covering hundreds of square kilometers (Nevitt 2008)....
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...In a recent study, Coleman et al. (2007) found that a fish and a crab that consume snails were attracted more to the odor of seaweeds recently attacked by snails than to the odor of unattacked or artificially damaged plants....
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TL;DR: Sperm limitation occurs in nature, and is a selection pressure in the mating strategy of female stone crabs, and the influence of risk of sperm limitation on female choice should be considered in studies of sexual selection by field observations and laboratory experiments, and in sexual selection models.
50 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...…mates, to stimulating or deterring copulation once mates are in contact, to sperm-egg chemical signaling that promotes or prevents fertilization when egg and sperm are nearby or in contact (Lonsdale et al. 1998, Kamio et al. 2002, Stebbing et al. 2003, Raffell et al. 2004, Sato & Goshima 2007)....
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...Sato & Goshima (2007) found that female stone crabs, Hapalogaster dentate, selected larger males on the basis of chemical signals, but could also distinguish between similar-sized males on the basis of whether or not they had sufficient versus depleted sperm reserves....
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...…herbivores that generally live on the plants they consume; Hay et al. (1987)] feeding and movement among hosts over scales of centimeters and meters (Coleman et al. 2007), but also appear to affect foraging by some sea birds over landscapes covering hundreds of square kilometers (Nevitt 2008)....
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TL;DR: This study developed a relatively rapid test of shelter choice in a 5000-l laboratory flume that simulated flow conditions in the spiny lobster’s natural environment, and used it to examine the shelter preference of the animals in response to a variety of odorants, which demonstrated specificity in the cues mediating sheltering behavior.
Abstract: Caribbean spiny lobsters display a diversity of social behaviors, one of the most prevalent of which is gregarious diurnal sheltering. Previous research has demon- strated that shelter selection is chemically mediated, but the source of release and the identity of the aggregation signal are unknown. In this study, we investigated the source and specificity of the aggregation signal in Caribbean spiny lobsters, Panulirus argus. We developed a relatively rapid test of shelter choice in a 5000-l laboratory flume that simulated flow conditions in the spiny lobster's natural environment, and used it to examine the shelter preference of the animals in response to a variety of odorants. We found that both males and females associated preferentially with shelters emanating conspecific urine of either sex, but not with shelters emanating seawater, food odors, or the scent of a predatory octopus. These results demonstrate specificity in the cues mediating sheltering behavior and show that urine is at least one source of the aggregation signal.
49 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...Recruitment to occupied shelters (and thus gregarious occupancy) is chemically mediated, with greater recruitment to shelters where conspecific urine is being released (Horner et al. 2006)....
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