Species Distribution Modelling

Background:

Global open ocean and deep seas (>200 m depth) occupy the majority of the habitat on Earth (Sutton et al., 2017) with total volume of more than 1.2 billion km3 (Rogers, 2015) and mean depth of 4.2 km. Mesopelagic, also known as a twilight zone of the global ocean (Ramirez-Llodra et al., 2010), represents the part of the ocean where surface light is still detectable during the daytime allowing organisms to distinguish diurnal and nocturnal cycles (Sutton, 2013), but is at a level low enough so that net primary production is no longer possible (Klevjer et al., 2012; Proud et al., 2017; Robinson et al., 2010). In this work, mesopelagic is referred to a zone in the ocean with depth range between 200 to 1,000 m. Many organisms inhabit mesopelgic zone. This work focuses on one part of the mesopelagic community: mesozooplankton and micronekton. Here, we define mesozooplankton as zooplankton with a size range of 0.2-20 mm and micronekton (that also includes macrozooplankton) are the organisms with a size range of 2-20 cm. Quantification of zooplankton over vertical and horizontal scales is essential to understanding pelagic food web structure and functioning (McIvor, 2011) and to predict vertical fluxes of organic matter to the deep ocean (Stemmann et al., 2008). Micronekton and mesozooplankton are known to fragment, re-mineralize and re-consolidate sinking particles through the water column (Turner, 2002; Stemmann et al., 2008) and contribute to CO2 removal from the atmosphere. Furthermore, mesozooplankton and micronekton form a critical link, transferring energy from phytoplankton to higher trophic levels (epipelagic and air-breathing organisms). For instance, krill, crustaceans and copepods are the prey of the mesopelagic fishes (Williams & Koslow, 1997; Williams et al., 2001). Krill and different mesopelagic fishes; in turn, are the important food source for seabirds, different species of seals, cephalopods, cetaceans and beaked whales (Hopkins et al., 1993; Sato & Benoit-Bird, 2017; Naito et al., 2017). Despite their ecological significance and considerable biomass, remarkably little is known about the mesopelagic micronekton and mesozooplankton distribution (Béhagle et al., 2015). For instance, the estimate of mesopelagic fish biomass is used in assessments of ecosystem function and biogeochemistry of the global ocean (Tréguer et al., 2013; Christensen et al., 2009) and is used in different ecosystem models for estimating the total fish biomass (Irigoien et al., 2014).

Experimental Design & Main Goals:

To our current knowledge, no work has been done to attempt to synthesize the available global estimates of the mesozooplankton community to explore the current state of knowledge or to perform global comparisons between the areas. We compiled the first global database using all available literature (published and unpublished) containing the information on mesopelagic species distribution and abundance. Although quite a volume of quantitative information is available on the distribution of different mesopelagic mesozooplankton and micronekton species, this quantitative information is hardly comparable between the regions as the data collected at the different time of year, time of day or by means of different sampling gear. All these factors (and many others such as net mouth area and type of organism sampled) can complicate the comparison between the areas. This work attempts to create a dataset with adjusted values of abundance that are brought to a standardized abundance values.