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: A null mutation in smcR (luxR) resulted in a defect in starvation survival, inhibition of starvation-induced maintenance of culturability that occurs when V. vulnificus is starved prior to low-temperature incubation, and increased expression of stationary-phase phenotypes.
Abstract: Vibrio vulnificus contains homologues of the V. harveyi luxR and luxS genes. A null mutation insmcR (luxR) resulted in a defect in starvation survival, inhibition of starvation-induced maintenance of culturability that occurs when V. vulnificusis starved prior to low-temperature incubation, and increased expression of stationary-phase phenotypes.
89 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...This inhibition occurs because halogenated furanones interfere with the bacteria’s signal-based regulatory systems that control surface motility, exoenzyme production, and biofilm formation/stability (Manefield et al. 1999, 2002; Rasmussen et al. 2000; McDougald et al. 2001)....
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TL;DR: The results suggest that the evolution of host preferences may depend more on the host value as a refuge from enemies than on minimizing the costs of tolerating plant secondary metabolites, which is especially true for marine systems.
Abstract: Previous investigations have shown that the sedentary amphipod Ampithoe longimana escapes consumers by selectively living on and eating chemically defended seaweeds in the genus Dictyota. However, A. longimana and Dictyota overlap only in the southern portion of the amphipod's range; Dictyota is not available to amphipods from more northerly regions. We used this disjunction in distribution to test the hypothesis that A. longimana populations co-occurring with Dictyota would have greater tolerance for the seaweed's chemical defenses and would display higher feeding preference for, and fitness on, the seaweed than would more northerly populations. We also evaluated the genetic vs. phenotypic basis of these patterns and attempted to detect trade-offs between tolerance for Dictyota and ability to use other plants as foods. Such geographic studies of herbivory have been conducted using terrestrial insects, but few studies have focused on other her- bivores, and this is especially true for marine systems. In multiple-choice feeding assays with both field-collected and laboratory-reared adults, a North Carolina population of A. longimana sympatric with Dictyota more readily fed on Dictyota and was more resistant to Dictyota's deterrent chemistry than was a Connecticut population from outside of Dic- tyota's geographic range. When raised on Dictyota menstrualis and D. ciliolata, A. lon- gimana juveniles from North Carolina grew faster, matured faster, and produced more reproductive females than did Connecticut juveniles. The differential tolerance for Dictyota has a genetic basis, as it was maintained through two generations grown to maturity in a common environment. When several northern and southern populations were assayed, they displayed similar regional differences in feeding preferences. Though southern juveniles had higher fitness onDictyota than northern juveniles, south- ern juveniles performed as well as northern juveniles when raised on seven other seaweeds, including seaweeds (e.g., Fucus vesiculosus and Sargassum filipendula ) that produce sec- ondary metabolites in a different class from those found in Dictyota. Thus, tolerating Dictyota did not incur detectable performance trade-offs when juveniles were confined to feeding on alternative seaweeds. Our results suggest that the evolution of host preferences may depend more on the host value as a refuge from enemies than on minimizing the costs of tolerating plant secondary metabolites.
89 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...The amphipod occurs from New England to the Caribbean, but Dictyota occurs only south of Virginia....
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...Although A. longimana populations from New England survived and grew relatively well on foods containing dictyols, consuming dictyols reduced fecundity dramatically; this was not the case for A. longimana populations that co-occurred with Dictyota: They survived, grew, and reproduced well despite the addition of dictyols to their foods (Cruz-Rivera & Hay 2003, Sotka & Hay 2002, Sotka et al. 2003)....
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...Thus, if evolving resistance to Dictyota chemical defenses is costly for the amphipod, then one expects that the populations that overlap with Dictyota (and can benefit from escaping fish predators by living on the alga) will be selected to tolerate its chemical defenses, whereas those from New England will not because they cannot benefit from escaping predators by associating with this seaweed....
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...When feeding and fitness of A. longimana populations from New England and populations from North Carolina were compared across numerous seaweeds, populations from New England avoided Dictyota relative to populations from North Carolina and those from North Carolina had higher fitness when cultured on Dictyota than did those from New England (Sotka & Hay 2002, Sotka et al. 2003)....
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...…from North Carolina were compared across numerous seaweeds, populations from New England avoided Dictyota relative to populations from North Carolina and those from North Carolina had higher fitness when cultured on Dictyota than did those from New England (Sotka & Hay 2002, Sotka et al. 2003)....
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TL;DR: The ecosystem-wide and potentially global consequences of aquatic chemical cues is an underappreciated topic that warrants additional attention and can be made that phytoplankton metabolites such as dimethyl sulfide (DMS) link interaction webs that span hundreds to thousands of kilometers.
Abstract: Aquatic organisms produce compounds that deter consumers, alter prey behavior, suppress or kill target and nontarget species, and dramatically affect food-web structure, community composition, and the rates and pathways of biogeochemical cycles. Toxins from marine and freshwater phytoplankton create health hazards for both aquatic and terrestrial species and can significantly affect human activities and the economic vitality of local communities. A reasonable case can be made that phytoplankton metabolites such as dimethyl sulfide (DMS) link interaction webs that span hundreds to thousands of kilometers and connect production from oceanic phytoplankton to desert cacti and coyotes via zooplankton, fishes, and sea birds. The possible role of DMS in global heat budgets expands this effect even further. The ecosystem-wide and potentially global consequences of aquatic chemical cues is an underappreciated topic that warrants additional attention.
83 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...Thus, chemical cues affect not only individual behavior and population-level processes, but also community organization and ecosystem function (e.g., Hay & Kubanek 2002, Pohnert et al. 2007)....
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...…systems (Gross 2003, Legrand et al. 2003), where they may help produce large-scale, ecosystem-level effects due to some dominant species forming toxic algal blooms that kill millions of fishes, thus altering local food webs and damaging coastal economies (Hay & Kubanek 2002, Paul et al. 2007)....
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...Developing ecologically realistic bioassays for these systems is more difficult than for benthic organisms (Hay et al. 1998, Hay & Kubanek 2002), but progress is being made (Pohnert et al. 2007) and better bioassay procedures will produce many new discoveries....
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TL;DR: Mate-finding behaviour in the marine copepod Centropages typicus was investigated by 3-dimensional video analysis and model considerations suggest that these pheromones are small molecules, e.g. amino acids, which represents only a small fraction of the females' ingestion and metabolic rate.
Abstract: Mate-finding behaviour in the marine copepod Centropages typicus was investigated by 3-dimensional video analysis. Females leave a chemical trail in their wake and a male intercept- ing a fresh trail initiates a characteristic tracking behaviour in which he increases his speed from ~10 to ~30 mm s -1 and races up the female trail while displaying a tight zigzag motion. Within sec- onds the male overtakes the female and attempts to catch her. Males faithfully follow even very con- voluted trails and successfully track down females after pursuing trails up to 31 s old and 17 cm long. The probability of detecting a trail is inversely related to trail age and length. Males often start track- ing female trails in the wrong direction before correcting themselves, and the frequency of direc- tional errors increases with increasing trail age. Complicated or disrupted signal trails may cause males to lose the trail. This induces a distinct signal-scanning behaviour characterised by further enhanced swimming speeds of 50 to 70 mm s -1 , and frequent shifts of direction. The male scans a restricted volume around the point where the trail was lost and often regains the trail and resumes normal tracking behaviour. This behaviour may help males follow trails that are broken by turbu- lence. A simple generic model of pheromone trails that is consistent with the tracking behaviour of males in C. typicus and other species of copepods was used to explore the characteristics of pheromone trails. Model considerations suggest that these pheromones are small molecules, e.g. amino acids, and that the investment in pheromone production, both in terms of elements and metabolic energy, represents only a small fraction of the females' ingestion and metabolic rate.
82 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...F or p er so na l u se o nl y. DMS tracking abilities vary across species within these seabirds and are correlated with behavioral, phylogenetic, and life history traits....
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...When males of the copepod Centropages typicus cross a pheromone trail left by a female, they increase their swimming speed by three- to sixfold, zigzag rapidly along the exact path taken by the female, rapidly overtake her, and attempt to mate (Bagoien & Kiorboe 2005)....
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TL;DR: Information on behavioural ecology of whale sharks is synthesised from the published literature and personal observations within the unifying framework of theoretical behavioural ecology, revealing opportunities to fill in critical knowledge gaps.
80 citations
"Marine chemical ecology: chemical s..." refers background in this paper
...These DMS signals for feeding are not restricted only to seabirds, but also seem to be used by reef fishes (DeBose & Nevitt 2008), harbor seals (Kowalewsky et al. 2006), and whale sharks (Martin 2007). www.annualreviews.org • Marine Chemical Ecology 195 A nn u....
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