Journal Article•
Marine benthic hypoxia: a review of its ecological effects and the behavioural responses of benthic macrofauna
About: This article is published in Oceanographic Literature Review.The article was published on 1996-01-01 and is currently open access. It has received 1963 citations till now. The article focuses on the topics: Benthic zone & Hypoxia (environmental).
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TL;DR: For example, a recent review of the early phase of the coastal eutrophication problem can be found in this article, where the authors suggest that the early (phase I) con- ceptual model was strongly influenced by limnologists, who began intense study of lake eutrophicication by the 1960s.
Abstract: A primary focus of coastal science during the past 3 decades has been the question: How does anthropogenic nutrient enrichment cause change in the structure or function of nearshore coastal ecosystems? This theme of environmental science is recent, so our conceptual model of the coastal eutrophication problem continues to change rapidly In this review, I suggest that the early (Phase I) con- ceptual model was strongly influenced by limnologists, who began intense study of lake eutrophication by the 1960s The Phase I model emphasized changing nutrient input as a signal, and responses to that signal as increased phytoplankton biomass and primary production, decomposition of phytoplankton- derived organic matter, and enhanced depletion of oxygen from bottom waters Coastal research in recent decades has identified key differences in the responses of lakes and coastal-estuarine ecosystems to nutrient enrichment The contemporary (Phase II) conceptual model reflects those differences and includes explicit recognition of (1) system-specific attributes that act as a filter to modulate the responses to enrichment (leading to large differences among estuarine-coastal systems in their sensitivity to nu- trient enrichment); and (2) a complex suite of direct and indirect responses including linked changes in: water transparency, distribution of vascular plants and biomass of macroalgae, sediment biogeochem- istry and nutrient cycling, nutrient ratios and their regulation of phytoplankton community composition, frequency of toxic/harmful algal blooms, habitat quality for metazoans, reproduction/growth/survival of pelagic and benthic invertebrates, and subtle changes such as shifts in the seasonality of ecosystem functions Each aspect of the Phase II model is illustrated here with examples from coastal ecosystems around the world In the last section of this review I present one vision of the next (Phase III) stage in the evolution of our conceptual model, organized around 5 questions that will guide coastal science in the early 21st century: (1) How do system-specific attributes constrain or amplify the responses of coastal ecosystems to nutrient enrichment? (2) How does nutrient enrichment interact with other stressors (toxic contaminants, fishing harvest, aquaculture, nonindigenous species, habitat loss, climate change, hydro- logic manipulations) to change coastal ecosystems? (3) How are responses to multiple stressors linked? (4) How does human-induced change in the coastal zone impact the Earth system as habitat for humanity and other species? (5) How can a deeper scientific understanding of the coastal eutrophication problem be applied to develop tools for building strategies at ecosystem restoration or rehabilitation?
2,658 citations
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TL;DR: The only way to eliminate Nr accumulation and stop the cascade is to convert Nr back to nonreactive N2, which leads to lag times in the continuation of the cascade.
Abstract: Human production of food and energy is the dominant continental process that breaks the triple bond in molecular nitrogen (N2) and creates reactive nitrogen (Nr) species. Circulation of anthropogenic Nr in Earth’s atmosphere, hydrosphere, and biosphere has a wide variety of consequences, which are magnified with time as Nr moves along its biogeochemical pathway. The same atom of Nr can cause multiple effects in the atmosphere, in terrestrial ecosystems, in freshwater and marine systems, and on human health. We call this sequence of effects the nitrogen cascade. As the cascade progresses, the origin of Nr becomes unimportant. Reactive nitrogen does not cascade at the same rate through all environmental systems; some systems have the ability to accumulate Nr, which leads to lag times in the continuation of the cascade. These lags slow the cascade and result in Nr accumulation in certain reservoirs, which in turn can enhance the effects of Nr on that environment. The only way to eliminate Nr accumul...
2,647 citations
TL;DR: In this article, a global assessment of the effects of inorganic nitrogen pollution in aquatic ecosystems is presented, with detailed multi-scale data, and three major environmental problems: (1) increasing the concentration of hydrogen ions in freshwater ecosystems without much acid-neutralizing capacity, resulting in acidification of those systems; (2) stimulating or enhancing the development, maintenance and proliferation of primary producers, leading to eutrophication of aquatic ecosystems; (3) reaching toxic levels that impair the ability of aquatic animals to survive, grow and reproduce.
1,753 citations
TL;DR: The important life-supporting role of hydrogen sulfide (H(2)S) has evolved from bacteria to plants, invertebrates, vertebrate, vertebrates, and finally to mammals, but over the centuries it had only been known for its toxicity and environmental hazard.
Abstract: The important life-supporting role of hydrogen sulfide (H2S) has evolved from bacteria to plants, invertebrates, vertebrates, and finally to mammals. Over the centuries, however, H2S had only been known for its toxicity and environmental hazard. Physiological importance of H2S has been appreciated for about a decade. It started by the discovery of endogenous H2S production in mammalian cells and gained momentum by typifying this gasotransmitter with a variety of physiological functions. The H2S-catalyzing enzymes are differentially expressed in cardiovascular, neuronal, immune, renal, respiratory, gastrointestinal, reproductive, liver, and endocrine systems and affect the functions of these systems through the production of H2S. The physiological functions of H2S are mediated by different molecular targets, such as different ion channels and signaling proteins. Alternations of H2S metabolism lead to an array of pathological disturbances in the form of hypertension, atherosclerosis, heart failure, diabetes...
1,560 citations
TL;DR: A broad comparative analysis showed that hypoxia thresholds vary greatly across marine benthic organisms and that the conventional definition of 2 mg O2/liter to designate waters as hypoxic is below the empirical sublethal and lethal O2 thresholds for half of the species tested.
Abstract: Hypoxia is a mounting problem affecting the world’s coastal waters, with severe consequences for marine life, including death and catastrophic changes. Hypoxia is forecast to increase owing to the combined effects of the continued spread of coastal eutrophication and global warming. A broad comparative analysis across a range of contrasting marine benthic organisms showed that hypoxia thresholds vary greatly across marine benthic organisms and that the conventional definition of 2 mg O2/liter to designate waters as hypoxic is below the empirical sublethal and lethal O2 thresholds for half of the species tested. These results imply that the number and area of coastal ecosystems affected by hypoxia and the future extent of hypoxia impacts on marine life have been generally underestimated. benthic community oxygen coastal ecosystems eutrophication impacts D issolved oxygen in coastal waters has changed drastically over the past decades, arguably more so than any other ecologically important variable (1, 2), leading to the widespread occurrence of hypoxia. An assessment of the literature shows that the number of coastal sites where hypoxia has been reported has increased with an exponential growth rate of 5.54% year 1 over time [Fig. 1 and supporting information (SI) Table S1]. Although this growth rate can be partially attributed to an increased observational effort, increasing the number of costal ecosystems monitored and the likelihood of detecting hypoxia therein, this growth also reflects an increase in the prevalence of hypoxia in different types of coastal ecosystems. Multiple reports from careful monitoring time series provide evidence for an unambiguous increase in the number of hypoxic zones and their extension, severity, and duration (3–6). This growth is expected to continue because the prevalence of hypoxia is forecast to increase further owing to the combined effects of eutrophication, leading to the excessive production of organic matter that increases the oxygen demand of coastal ecosystems (7), and the increase in temperature caused by climate change, which enhances the respiratory oxygen demand of the organisms (8), reduces oxygen solubility (9), and reduces the ventilation of coastal waters by affecting stratification patterns (10).
1,453 citations