Seagrasses comprise <0.02% of the angiosperm flora, representing a surprisingly small number of species (about 50, Table 1.1) compared with any other group of marine organisms. The limited species membership of the seagrass flora has directed some (still limited) efforts to the study of their origin and their evolution in an attempt to account for this phenomenon. A second path of research has tried to find clues for the paucity of species by studying the stress factors constraining angiosperm life in the sea. This second approach has driven much effort towards the analysis of seagrass distribution and the definition of the habitat requirements of seagrasses. The attention these issues have received extends beyond scholarly concerns, for seagrasses are, despite their limited diversity, important contributors to coastal marine ecosystems, both locally and at the global scale. In this chapter we shall provide an overview of the origin, evolution and present diversity of extant seagrasses, and describe their present distribution and the basic requirements that delimit their possible habitats. The definition of how seagrass distribution is regulated leads, in turn, to the assessment of their global extent and, from this, to the evaluation of the role seagrasses play on the global ocean ecosystem.
Oceans have become substantially noisier since the Industrial Revolution. Shipping, resource exploration, and infrastructure development have increased the anthrophony (sounds generated by human activities), whereas the biophony (sounds of biological origin) has been reduced by hunting, fishing, and habitat degradation. Climate change is affecting geophony (abiotic, natural sounds). Existing evidence shows that anthrophony affects marine animals at multiple levels, including their behavior, physiology, and, in extreme cases, survival. This should prompt management actions to deploy existing solutions to reduce noise levels in the ocean, thereby allowing marine animals to reestablish their use of ocean sound as a central ecological trait in a healthy ocean.
To assess the efforts deployed by different nations and territories in sequencing SARS-CoV-2 isolates, thus enabling detection of variants, known and novel, of concern.The sources of over one million full genome sequences of SARS-CoV-2 virus available in the COVID-19 virus Mutation Tracker (CovMT) were analyzed to determine the number of variants in the RBD region of the genome determining infectivity detected in the various nations and territories.The number of detected variants increased as the square root of sequencing effort by nations. Eight nations have contributed 79% of all SARS-CoV-2 isolates that have been sequenced, with two-thirds of all unique variants, adding to 1118 RBD variants, reported by five nations. The median number of sequenced isolates required to detect, on average, one novel RBD variant is 24.05, which is a threshold achieved by 70 nations.Many developing nations have not contributed any sequences due to lack of capacity. This poses a risk of dangerous virus variants in these under-sampled regions spreading globally before being detected. A collaborative program to sequence SARS-CoV-2 isolates, and other pathogens of concern, is needed to monitor, track, and control the pandemic.
Understanding movement of marine megafauna across the ocean is largely based on approaches and models based on analysis of tracks of single animals. While this has led to major progress, the possibility of concerted group dynamics has not been sufficiently examined, possibly due to challenges in exploring massive amounts of data required to this end. Here we report a sonification experiment, where the collective movement of northern elephant seals (Mirounga angustirostris) was explored by coding their group dynamics into sound. Specifically, we converted into sound data derived from a tagging program involving a total of 321 tagged animals tracked over a decade, between 20 February 2004 and 30 May 2014, consisting of an observation period of 90063 hours, composed of 1,027,839 individual positions. The data parameters used to provide the sound are position (longitude) and spread (degree of displacement taken for the active group). These data parameters are mapped to the sonic parameters of frequency (pitch) and amplitude (volume), respectively. Examination of the resulting sound revealed features of motion that translate into specific patterns in space. The serial departure of elephant seals to initiate their trips into waves is clearly reflected in the addition of tonalities, with coherent swimming of the animals conforming a wave reflected in the modulated fluctuations in volume, suggesting coordinated fluctuations in dispersion of the wave. Smooth changes in volume, coordinated with pitch variability, indicate that the animals spread out as they move further away from the colony, with one or a few animals exploring an ocean area away from that explored by the core wave. The shift in volume and pitch also signals at group coordination in initiating the return home. Coordinated initiation of the return to the colony is also clearly revealed by the sonification, as reflected in an increase in volume and pitch of the notes denoting the movement of each animal in a migration wave. This sonification reveals clear patterns of covariation in movement data, which drivers and triggers, whether intrinsic or environental, cannot be elucidated here but allow to formulate a number of non-trivial questions on the synchronized nature of group
The relative contributions of lake characteristics (i.e. alkalinity, chlorophyll A concentration, total phosphorus concentration, conductivity, and morphometry) and site characteristics (i.e. depth, littoral slope, exposure to waves, and underwater light levels) to the variability in submerged biomass were examined in 25 Canadian and American lakes. Lake-average submerged biomass is a function of water alkalinity and the lake-average littoral slope whereas site-specific biomass is a function of both site and lake characteristics. Plant biomass decreased with increasing slope and wave exposure and increased with increasing alkalinity and light levels. However, these relationships are complex because submerged biomass is also influenced by threshold phenomena (e.g. critical littoral slopes and transparency-dependent critical depths) that set limits to macrophyte colonization and because the relative contributions of the most relevant environmental factors studied (i.e. littoral slope, exposure, water transparency, and alkalinity) are depth dependent. By demonstrating the importance of lake-average and site-specific scales of variation and the existence of noncontinuous (e.g. threshold) regulation mechanisms the findings provide a new conceptual framework for the study of the relationship between submerged macrophytes, and their associated biota as well as their environment.
