Ecosystem function and services provided by the deep sea

The deep sea is often viewed as a vast, dark, remote, and inhospitable environment, yet the deep ocean and seafloor are crucial to our lives through the services that they provide. Our understanding of how the deep sea functions remains limited, but when treated synoptically, a diversity of supporting, provisioning, regulating and cultural services becomes apparent. The biological pump transports carbon from the atmosphere into deep-ocean water masses that are separated over prolonged periods, reducing the impact of anthropogenic carbon release. Microbial oxidation of methane keeps another potent greenhouse gas out of the atmosphere while trapping carbon in authigenic carbonates. Nutrient regeneration by all faunal size classes provides the elements necessary for fueling surface productivity and fisheries, and microbial processes detoxify a diversity of compounds. Each of these processes occur on a very small scale, yet considering the vast area over which they occur they become important for the global functioning of the ocean. The deep sea also provides a wealth of resources, including fish stocks, enormous bioprospecting potential, and elements and energy reserves that are currently being extracted and will be increasingly important in the near future. Society benefits from the intrigue and mystery, the strange life forms, and the great unknown that has acted as a muse for inspiration and imagination since near the beginning of civilization. While many functions occur on the scale of microns to meters and timescales up to years, the derived services that result are only useful after centuries of integrated activity. This vast dark habitat, which covers the majority of the globe, harbour processes that directly impact humans in a variety of ways; however, the same traits that differentiate it from terrestrial or shallow marine systems also result in a greater need for integrated spatial and temporal understanding as it experiences increased use by society. In this manuscript we aim to provide a foundation for informed conservation and management of the deep sea by summarizing the important role of the deep sea in society.

The origin and evolution of synaptic proteins - choanoflagellates lead the way.

The origin of neurons was a key event in evolution, allowing metazoans to evolve rapid behavioral responses to environmental cues. Reconstructing the origin of synaptic proteins promises to reveal their ancestral functions and might shed light on the evolution of the first neuron-like cells in metazoans. By analyzing the genomes of diverse metazoans and their closest relatives, the evolutionary history of diverse presynaptic and postsynaptic proteins has been reconstructed. These analyses revealed that choanoflagellates, the closest relatives of metazoans, possess diverse synaptic protein homologs. Recent studies have now begun to investigate their ancestral functions. A primordial neurosecretory apparatus in choanoflagellates was identified and it was found that the mechanism, by which presynaptic proteins required for secretion of neurotransmitters interact, is conserved in choanoflagellates and metazoans. Moreover, studies on the postsynaptic protein homolog Homer revealed unexpected localization patterns in choanoflagellates and new binding partners, both which are conserved in metazoans. These findings demonstrate that the study of choanoflagellates can uncover ancient and previously undescribed functions of synaptic proteins.

The Impact of Polystyrene Microplastics on Feeding, Function and Fecundity in the Marine CopepodCalanus helgolandicus

Microscopic plastic debris, termed “microplastics”, are of increasing environmental concern. Recent studies have demonstrated that a range of zooplankton, including copepods, can ingest microplastics. Copepods are a globally abundant class of zooplankton that form a key trophic link between primary producers and higher trophic marine organisms. Here we demonstrate that ingestion of microplastics can significantly alter the feeding capacity of the pelagic copepod Calanus helgolandicus. Exposed to 20 μm polystyrene beads (75 microplastics mL–1) and cultured algae ([250 μg C L–1) for 24 h, C. helgolandicus ingested 11% fewer algal cells (P = 0.33) and 40% less carbon biomass (P < 0.01). There was a net downward shift in the mean size of algal prey consumed (P < 0.001), with a 3.6 fold increase in ingestion rate for the smallest size class of algal prey (11.6–12.6 μm), suggestive of postcapture or postingestion rejection. Prolonged exposure to polystyrene microplastics significantly decreased reproductive output, but there were no significant differences in egg production rates, respiration or survival. We constructed a conceptual energetic (carbon) budget showing that microplastic-exposed copepods suffer energetic depletion over time. We conclude that microplastics impede feeding in copepods, which over time could lead to sustained reductions in ingested carbon biomass.

Use Of Micro-Stereology And Quantitative Cyto-Chemistry To Determine The Effects Of Crude Oil-Derived Aromatic-Hydrocarbons On Lysosomal Structure And Function In A Marine Bivalve Mollusk Mytilus-Edulis

The marine bivalve mollusc,Mytilus edulis (blue mussel), is a noted accumulator of many environmental pollutants and is increasingly used for the chemical and biological assessment of environmental impact. The toxic effects of crude oil-derived aromatic hydrocarbons (30 μg/l total hydrocarbons) on the lysosomal-vacuolar system of the digestive cells have been investigated in cryostat sections of hexane-frozen digestive glands. Exposure to aromatic hydrocarbons reduced the cytochemically determined latency of lysosomal β-N-acetylhexosaminidase; lysosomal volume density and surface density increased while the numerical density decreased. Experimental exposure resulted in the formation of very large lysosomes which are believed to be largely autophagic in function and these results indicate a significant structural and functional disturbance of digestive cell lysosomes in response to hydrocarbons.

Fundamental shift in vitamin B12 eco-physiology of a model alga demonstrated by experimental evolution.

A widespread and complex distribution of vitamin requirements exists over the entire tree of life, with many species having evolved vitamin dependence, both within and between different lineages. Vitamin availability has been proposed to drive selection for vitamin dependence, in a process that links an organism's metabolism to the environment, but this has never been demonstrated directly. Moreover, understanding the physiological processes and evolutionary dynamics that influence metabolic demand for these important micronutrients has significant implications in terms of nutrient acquisition and, in microbial organisms, can affect community composition and metabolic exchange between coexisting species. Here we investigate the origins of vitamin dependence, using an experimental evolution approach with the vitamin B(12)-independent model green alga Chlamydomonas reinhardtii. In fewer than 500 generations of growth in the presence of vitamin B(12), we observe the evolution of a B(12)-dependent clone that rapidly displaces its ancestor. Genetic characterization of this line reveals a type-II Gulliver-related transposable element integrated into the B(12)-independent methionine synthase gene (METE), knocking out gene function and fundamentally altering the physiology of the alga.

Evolution of the diatoms: major steps in their evolution and a review of the supporting molecular and morphological evidence.

Over the years, many reviews of different aspects of diatom biology, ecology and evolution have appeared. Since 1993 many molecular trees have been produced to infer diatom phylogeny. In 2004, Medlin & Kaczmarska revised the systematics of the diatoms based on more than 20 years of consistent recovery of two major clades of diatoms that did not correspond to a traditional concept of centrics and pennates and established three classes of diatoms: Clade 1 = Coscinodiscophyceae (radial centrics) and Clade 2 = Mediophyceae (polar centrics + radial Thalassiosirales) and Bacillariophyceae (pennates). However, under certain analytical conditions, an alternative view of diatom evolution, a grades of clades, has been recovered that suggests a gradual evolution from centric to pennate symmetry. These two schemes of diatom evolution are evaluated in terms of whether or not the criteria advocated by Medlin & Kaczmarska that should be met to recover monophyletic classes have been used. The monophyly of the three diatom classes can only be achieved if (1) a secondary structure of the small subunit (SSU) rRNA gene was used to construct the alignment and not an alignment based on primary structure and (2) multiple outgroups were used. These requirements have not been met in each study of diatom evolution; hence, the grade of clades, which is useful in reconstructing the sequence of evolution, is not useful for accepting the new classification of the diatoms. Evidence for how these two factors affect the recovery of the three monophyletic classes is reviewed here. The three classes have been defined by clear morphological differences primarily based on gametangia and auxospore ontogeny and envelope structure, the presence or absence of a structure (tube process or sternum) associated with the annulus and the location of the cribrum in those genera with loculate areolae. New evidence supporting the three clades is reviewed. Other features of the cell are examined to determine whether they can also be used to support the monophyly of the three classes.

Evolution of the diatoms: major steps in their evolution and a review of the supporting molecular and morphological evidence.

Over the years, many reviews of different aspects of diatom biology, ecology and evolution have appeared. Since 1993 many molecular trees have been produced to infer diatom phylogeny. In 2004, Medlin & Kaczmarska revised the systematics of the diatoms based on more than 20 years of consistent recovery of two major clades of diatoms that did not correspond to a traditional concept of centrics and pennates and established three classes of diatoms: Clade 1 = Coscinodiscophyceae (radial centrics) and Clade 2 = Mediophyceae (polar centrics + radial Thalassiosirales) and Bacillariophyceae (pennates). However, under certain analytical conditions, an alternative view of diatom evolution, a grades of clades, has been recovered that suggests a gradual evolution from centric to pennate symmetry. These two schemes of diatom evolution are evaluated in terms of whether or not the criteria advocated by Medlin & Kaczmarska that should be met to recover monophyletic classes have been used. The monophyly of the three diatom classes can only be achieved if (1) a secondary structure of the small subunit (SSU) rRNA gene was used to construct the alignment and not an alignment based on primary structure and (2) multiple outgroups were used. These requirements have not been met in each study of diatom evolution; hence, the grade of clades, which is useful in reconstructing the sequence of evolution, is not useful for accepting the new classification of the diatoms. Evidence for how these two factors affect the recovery of the three monophyletic classes is reviewed here. The three classes have been defined by clear morphological differences primarily based on gametangia and auxospore ontogeny and envelope structure, the presence or absence of a structure (tube process or sternum) associated with the annulus and the location of the cribrum in those genera with loculate areolae. New evidence supporting the three clades is reviewed. Other features of the cell are examined to determine whether they can also be used to support the monophyly of the three classes.