Aggregating a Plankton Food Web: Mathematical versus Biological Approaches

Species are embedded in a web of intricate trophic interactions. Understanding the functional role of species in food webs is of fundamental interests. This is related to food web position, so positional similarity may provide information about functional overlap. Defining and quantifying similar trophic functioning can be addressed in different ways. We consider two approaches. One is of mathematical nature involving network analysis where unique species can be defined as those whose topological position is very different to others in the same food web. A species is unique if it has very different connection pattern compared to others. The second approach is of biological nature, based on trait-based aggregations. Unique species are not easy to aggregate with others because their traits are not in common with the ones of most others. Our goal here is to illustrate how mathematics can provide an alternative perspective on species aggregation, and how this is related to its biological counterpart. We illustrate these approaches using a toy food web and a real food web and demonstrate the sensitive relationships between those approaches. The trait-based aggregation focusing on the trait values of size (sv) can be best predicted by the mathematical aggregation algorithms

Plankton under Pressure: How Water Conditions Alter the Phytoplankton–Zooplankton Link in Coastal Lagoons

Transitional waters (TWs), such as coastal lagoons, are bodies of surface water at the transition between saline and freshwater domains. These environments play a vital role in guaranteeing ecosystem services, including provision of food, protection against meteorological events, as anthropogenic carbon sinks, and in filtering of pollutants. Due to the escalating overpopulation characterising coastlines worldwide, transitional systems are over-exploited, degraded, and reduced in their macroscopic features. However, information on the impact of anthropogenic pressures on planktonic organisms in these systems is still scanty and fragmented. Herein, we summarise the literature, with a special focus on coastal lagoons undergoing anthropogenic pressure. Specifically, we report on the implications of human impacts on the ecological state of plankton, i.e., a fundamental ecological component of aquatic ecosystems. Literature information indicates that human forces may alter ecosystem structures and functions in coastal lagoons, as in other TWs such as estuaries, hampering the phytoplankton–zooplankton link, i.e., the main trophic process occurring in those communities, and which sustains aquatic productivity. Changes in the dominance and lifestyle of key planktonic players, plus the invasion of ‘alien’ species, and consequent regime shifts, are among the most common outcomes of human disturbance

Intersecting Ecosystem Services Across the Aquatic Continuum: From Global Change Impacts to Local, and Biologically Driven, Synergies and Trade-Offs

The study of ecosystem services requires the integration of different observational points. This is particularly true in Water, as this element continuously cycles, increasing chances of interaction among services originating in different ecosystems. However, aquatic scientists historically approached the study of inland/freshwater and open/marine waters in different ways and this cultural division potentially hampers integrative approaches. Herein, we explored the literature pertaining to ecosystem services across the last 23 years, analysing 4,590 aquatic papers. By aggregating and intersecting topics included in this papers’ collection using text-mining and topical network approaches, we saw that the study of local environmental conditions (e.g., river estuary management) and synergies and trade-offs between services (e.g., carbon sequestration and water purification) can display several potential conceptual links between freshwater and marine sciences. Our analyses suggest that to intersect ecosystem services across the aquatic continuum, the conceptual integration between marine and freshwater science must be reinforced, especially at the interface between different “salinity realms.” Such integration should adopt a “system thinking” perspective, in which the focus is on multiple socio-ecological processes giving rise to interactions that are (i) biologically mediated, (ii) potentially conflicting, and (iii) entangled within networks.ISSN:2296-701

Structural and Functional Characterization of Lipoxygenases from Diatoms by Bioinformatics and Modelling Studies

Lipoxygenases make several biological functions in cells, based on the products of the catalyzed reactions. In diatoms, microalgae ubiquitous in aquatic ecosystems, lipoxygenases have been noted for the oxygenation of fatty acids with the production of oxylipins, which are involved in many physiological and pathological processes in marine organisms. The interest in diatoms’ lipoxygenases and oxylipins has increased due to their possible biotechnological applications, ranging from ecology to medicine. We investigated using bioinformatics and molecular docking tools the lipoxygenases of diatoms and the possible interaction with substrates. A large-scale analysis of sequence resources allowed us to retrieve 45 sequences of lipoxygenases from diatoms. We compared and analyzed the sequences by multiple alignments and phylogenetic trees, suggesting the possible clustering in phylogenetic groups. Then, we modelled the 3D structure of representative enzymes from the different groups and investigated in detail the structural and functional properties by docking simulations with possible substrates. The results allowed us to propose a classification of the lipoxygenases from diatoms based on their sequence features, which may be reflected in specific structural differences and possible substrate specificity

Building weighted networks for plankton communities from semi-quantitative data

Quantitative weighted network models are approaches widely used for understanding properties of the system. Although plankton community data in terms of composition and abundance are widely available, additional semi-quantitative ecological information are needed to build weighted networks. The goal of this study is the definition of an approach for developing quantitative networks from semi-quantitative data of plankton communities. The approach is based on a controlled iterative process that is used to develop synthetic networks that are then tested for realism using simple and general emerging properties by node and by the whole network as validating tests. We used realistic ranges for metabolic parameters of plankton community and we have defined semiquantitative indications of the strength of interactions between each taxa. An iterative MCMC approach was used by extracting random values for parameters from their range, through a uniform distribution, and assigning random quantitative values of diet proportions. A large group of valid models (ensemble of 1000 networks) were obtained for two different years for the Venice lagoon as a case study. Whole network indicators were applied to valid models. Preliminary results indicate a stressed system, dominated by detritus fluxes, so with a low mean trophic level and a high efficiency

Planktonic ecological networks support quantification of changes in ecosystem health and functioning

Abstract Plankton communities are the foundation of marine food webs and have a large effect on the dynamics of entire ecosystems. Changes in physicochemical factors strongly influence planktonic organisms and their turnover rates, making their communities useful for monitoring ecosystem health. We studied and compared the planktonic food webs of Palude della Rosa (Venice Lagoon, Italy) in 2005 and 2007. The food webs were developed using a novel approach based on the Monte Carlo random sampling of parameters within specific and realistic ranges to derive 1000 food webs for July of each year. The consumption flows involving Strombididae, Evadne spp. and Podon spp. were identified as the most important in splitting food webs of the July of the two years. Although functional nodes (FNs) differed both in presence and abundance in July of the two years, the whole system indicators showed very similar results. Sediment resuspension acted as a source of stress for the Venice Lagoon, being the most used resource by consumers while inhibiting primary producers by increasing water turbidity. Primary production in the water column was mainly generated by benthic FNs. Although the system was near an equilibrium point, it tended to increase its resilience at the expense of efficiency due to stress. This study highlights the role of plankton communities, which can serve to assess ecosystem health