Rethinking research: the role of tradition in the study of marine invertebrates

Scientific tradition is a key-element behind innovation and novelty in science. Relying on tradition provides a sense of security for the individual researcher but may also hamper scientific progress. By rethinking and reformulating previously stated research-topics and questions, science can profit from already existing data and knowledge. For this, however, a conceptual framework for critical thinking must exist for exchange of scientific ideas and findings. Tradition and critical thinking supply the framework for understanding data collected today in relation to previously accumulated information and scientific knowledge. This paper reflects upon these processes from the perspective of marine biological studies on soft-sediment invertebrates in Finland during the past 100 years exemplified by the works of Sven G. Segerstråle, with his education rooted in the old and traditional, and yet daring to think and work in innovative pathways

Food web positioning of a recent coloniser: the North American Harris mud crab Rhithropanopeus harrisii (Gould, 1841) in the northern Baltic Sea

Identifying resource use and functional traits of non-indigenous species are promising means to increase the ability to predict ecological consequences of invasions. One of the most widely spread brachyuran crab species, and a recent invader in the northern Baltic Sea, is the North American Harris mud crab, Rhithropanopeus harrisii (Gould, 1841). Although spread, establishment, and population structure have been studied for this species, little is known about its role and impact in a new environment. We investigated the position and role of R. harrisii in the coastal food web by combining spatial and temporal estimates of trophic position using stable isotopes (δ13C and δ15N), with short-term food- and habitat-choice experiments. We observed a stable pattern in the trophic position between two environmentally different locations in the Archipelago Sea over the production season. The identification of a natural breakpoint in carbon stable isotopes at the size of 12 mm carapace width suggested a presence of an ontogenetic diet shift, which was confirmed by isotope signatures positioning large R. harrisii among secondary consumers and small individuals with primary consumers. The generalist consumer nature of R. harrisii and preference for structured habitat was supported by an active habitat and food choice, revealing no preference for prey species (polychaetes versus amphipod), but selection of brown algae over bare mud. To broaden the understanding of the functional role of R. harrisii, we combined our findings with other known biological and ecological traits of the species and qualitatively compared these to characteristics of other benthic organisms in the northern Baltic Sea, suggesting a general similarity in traits

Habitat utilization and feeding ecology of small round goby in a shallow brackish lagoon

We examined small-scale distribution and feeding ecology of a non-native fish species, round goby (Neogobius melanostomus (Pallas, 1814)), in different habitats of a coastal lagoon situated in the south-western Baltic Sea. First observations of round goby in this lagoon were reported in 2011, 3 years before the current study was conducted, and information on this species’ basic ecology in different habitats is limited. We found that mainly juvenile round gobies are non-randomly distributed between habitats and that abundances potentially correlate positively with vegetation density and thus structural complexity of the environment. Abundances were highest in shallower, more densely vegetated habitats indicating that these areas might act as a refuge for small round gobies by possibly offering decreased predation risk and better feeding resources. Round goby diet composition was distinct for several length classes suggesting an ontogenetic diet shift concerning crustacean prey taxa between small (≤ 50 mm total length, feeding mainly on zooplankton) and medium individuals (51–100 mm, feeding mainly on benthic crustaceans) and another diet shift of increasing molluscivory with increasing body size across all length classes. Differences in round goby diet between habitats within the smallest length class might potentially be related to prey availability in the environment, which would point to an opportunistic feeding strategy. Here, we offer new insights into the basic ecology of round goby in littoral habitats, providing a better understanding of the ecological role of this invasive species in its non-native range, which might help to assess potential consequences for native fauna and ecosystems

A new reality for coastal zoobenthos: long-term changes (1958–2005) in a shallow sheltered bay

The zoobenthos in the narrow and shallow brackish-water bay Kuristenlahti in Airisto (SW Finnish archipelago) was studied in 2005, and the results were compared to unpublished data from 1958–1965 from the same area in order to analyse the long-term and spatial variability of the fauna. Observations were made at seven different stations. The length-frequency distribution was recorded for the bivalve Macoma balthica to study recruitment and survival in this specific environment. Significant changes in species composition, diversity, abundance and biomass, corresponding to changes in the environment, had occurred over time. After 1965 a smaller port for leisure boats had been built in the bay, and a fish farmwas active for some years at the seaside of the entrance to the bay. These events, combined with severe eutrophication due to the nutrient load from the agriculture close to the bay have affected the zoobenthos negatively, and the zoobenthic assemblages of today are significantly different from and poorer than those found in the bay 40–45 years ago. This study highlights the importance and value of available referencedata for the evaluation of the present-day environmental status

Brackish-water benthic fauna under fluctuating environmental conditions : The role of eutrophication, hypoxia, and global change

We studied the spatio-temporal impacts of physical and chemical environmental variables (depth, sediment type, salinity, temperature, oxygen, total phosphorus, and total nitrogen) on soft-sediment zoobenthos in the open coastal Gulf of Finland during 2001–2015. The study included 55 sampling-stations covering the east-west gradient of the Finnish coastal zone. The chosen environmental variables significantly influenced the distribution of the species in space and over time. Some zoobenthic taxa formed assemblages with each other, occurring in similar environmental conditions, while Gammarus spp. and Chironomidae clearly differed from other taxa in regards to ecological requirements. We showed the critical influence of oxygen (normoxia, hypoxia, anoxia) on individual species, some better adapted to low oxygen conditions (e.g., Chironomidae) than others (e.g., Monoporeia affinis). The nutrient concentrations in the surface sediment also significantly affected the benthic assemblage patterns. The number of species in space and time increased with increasing oxygen concentrations. This study clearly shows that in order to maintain healthy marine communities, it is essential to counteract excess nutrient inputs and their indirect effects on sufficient O2 conditions for the benthic habitats

Context-dependent consequences of Marenzelleria spp. (Spionidae:Polychaeta) invasion for nutrient cycling in the Northern Baltic Sea

Marenzelleria spp. are among the most successful non-native benthic species in the Baltic Sea. These burrowing polychaetes dig deeper than most native Baltic species, performing previously lacking ecosystem functions. We examine evidence from experiments, field sampling and modelling that the introduction of Marenzelleria spp. affects nutrient cycling and biogeochemical processes at the sediment water interface. Over longer time scales, bioirrigation by Marenzelleria spp. has the potential to increase phosphorus retention in bottom deposits because of deeper oxygen penetration into sediments and formation of a deeper oxidized layer. In contrast, nitrogen fluxes from the sediment increase. As a consequence of a decline of the phosphate concentration and/or rising nitrogen/phosphorus ratio, some Northern Baltic ecosystems may experience improvement of the environment because of mitigation of eutrophication and harmful cyanobacteria blooms. Although it is difficult to unambiguously estimate the ecosystem-level consequences of invasion, in many cases it could be considered as positive due to increased structural and functional diversity. The long-term interactions with the native fauna still remain unknown, however, and in this paper we highlight the major knowledge gaps. (C) 2015 Institute of Oceanology of the Polish Academy of Sciences., Production and hosting by Elsevier Sp. z o.o.Peer reviewe

Ecological coherence of Marine Protected Areas: New tools applied to the Baltic Sea network

Spatial connectivity is an essential process to consider in the design and assessment of Marine Protected Areas (MPAs). To help maintain and restore marine populations and communities MPAs should form ecologically coherent networks. How to estimate and implement connectivity in MPA design remains a challenge. Here a new theoretical framework is presented based on biophysical modelling of organism dispersal, combined with a suite of tools to assess different aspects of connectivity that can be integrated in MPA design. As a demonstration, these tools are applied to an MPA network in the Baltic Sea (HELCOM MPA). The tools are based on the connectivity matrix, which summarizes dispersal probabilities, averaged over many years, between all considered areas in the geographic target area. The biophysical model used to estimate connectivity included important biological traits that affect dispersal patterns where different trait combinations and habitat preferences will produce specific connectivity matrices representing different species. Modelled connectivity matrices were used to assess local retention within individual MPAs, which offers indications about the adequacy of size when MPAs are considered in isolation. The connectivity matrix also provides information about source areas to individual MPAs, e.g. sources of larvae or pressures such as contaminants. How well several MPAs act as a network was assessed within a framework of eigenvalue perturbation theory (EPT). With EPT, the optimal MPA network with respect to connectivity can be identified. In addition, EPT can suggest optimal extensions of existing MPA networks to enhance connectivity. Finally, dispersal barriers can be identified based on the connectivity matrix, which may suggest boundaries for management units. The assessment of connectivity for the HELCOM MPA are discussed in terms of possible improvements, but the tools presented here could be applied to any region

Environmental abundances of the non-native round goby Neogobius melanostomus influence feeding of native fish predators

The authors assessed the importance of the round goby Neogobius melanostomus as prey for three native predatory fish species, Atlantic cod Gadus morhua, European perch Perca fluviatilis and northern pike Esox lucius, in a northern and southern area of the Baltic Proper, using a combination of visual analysis and DNA metabarcoding of predator stomach contents. To explore the influence of environmental abundances of N. melanostomus on predation, they related the occurrence of N. melanostomus in predator diets to its abundance in survey fishing. Gadus morhua and E. lucius in the southern area showed the highest tendency to feed on N. melanostomus when it was abundant, as N. melanostomus occurred in up to 100% of stomachs and constituted up to 88% of the total diet volume proportion. The diet contribution of N. melanostomus was associated with N. melanostomus abundances for G. morhua and E. lucius, and when N. melanostomus was abundant, these predators exhibited lower prey richness and a higher degree of piscivory. G. morhua and P. fluviatilis also fed less on crustacean prey when N. melanostomus was abundant. The high importance of N. melanostomus in diets of native fish predators may modify indirect interactions between N. melanostomus and native prey species in invaded coastal communities