Offshore wind farms (OWFs) act as artificial reefs, attracting high abundances of fish, which could potentially increase their local production. This study investigates the feeding ecology of fish ...species that abundantly occur at artificial habitats, such as OWFs, by examining the short- and the long-term dietary composition of five species: the benthopelagic
Gadus morhua
and
Trisopterus luscus
, the pelagic
Scomber scombrus
and
Trachurus trachurus
, and the benthic
Myoxocephalus scorpioides
. We conducted combined stomach content and stable isotope analyses to examine the short- and the time-integrated dietary composition, respectively. Our results indicated that benthopelagic and benthic species utilize artificial reefs, such as OWFs, as feeding grounds for a prolonged period, since both analyses indicated that they exploit fouling organisms occurring exclusively on artificial hard substrates.
Trachurus trachurus
only occasionally uses artificial reefs as oases of highly abundant resources.
Scomber scombrus
does not feed on fouling fauna and therefore its augmented presence in OWFs is probably related to reasons other than the enhanced food availability. The long-termed feeding preferences of benthic and benthopelagic species contribute to the hypothesis that the artificial reefs of OWFs could potentially increase the fish production in the area. However, this was not supported for the pelagic species.
The identification of free-living marine nematodes is difficult because of the paucity of easily scorable diagnostic morphological characters. Consequently, molecular identification tools could solve ...this problem. Unfortunately, hitherto most of these tools relied on 18S rDNA and 28S rDNA sequences, which often lack sufficient resolution at the species level. In contrast, only a few mitochondrial COI data are available for free-living marine nematodes. Therefore, we investigate the amplification and sequencing success of two partitions of the COI gene, the M1-M6 barcoding region and the I3-M11 partition.
Both partitions were analysed in 41 nematode species from a wide phylogenetic range. The taxon specific primers for the I3-M11 partition outperformed the universal M1-M6 primers in terms of amplification success (87.8% vs. 65.8%, respectively) and produced a higher number of bidirectional COI sequences (65.8% vs 39.0%, respectively). A threshold value of 5% K2P genetic divergence marked a clear DNA barcoding gap separating intra- and interspecific distances: 99.3% of all interspecific comparisons were >0.05, while 99.5% of all intraspecific comparisons were <0.05 K2P distance.
The I3-M11 partition reliably identifies a wide range of marine nematodes, and our data show the need for a strict scrutiny of the obtained sequences, since contamination, nuclear pseudogenes and endosymbionts may confuse nematode species identification by COI sequences.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Offshore wind farms (OWFs) are proliferating globally. The submerged parts of their structures act as artificial reefs, providing new habitats and likely affecting fisheries resources. While ...acknowledging that the footprints of these structures may result in loss of habitat, usually soft sediment, we focus on how the artificial reefs established by OWFs affect ecosystem structure and functioning. Structurally, the ecological response begins with high diversity and biomass in the flora and fauna that gradually colonize the complex hard substrate habitat. The species may include nonindigenous ones that are extending their spatial distributions and/or strengthening populations, locally rare species (e.g., hard substrate-associated fish), and habitat-forming species that further increase habitat complexity. Functionally, the response begins with dominant suspension feeders that filter organic matter from the water column. Their fecal deposits alter the surrounding seafloor communities by locally increasing food availability, and higher trophic levels (fish, birds, marine mammals) also profit from locally increased food availability and/or shelter. The structural and functional effects extend in space and time, impacting species differently throughout their life cycles. Effects must be assessed at those larger spatiotemporal scales.
The presence of biofouling communities in very large densities in offshore wind farms (OWFs) generates broad effects on the structure and functioning of the marine ecosystem, yet the mechanisms ...behind the temporal development of these communities remain poorly understood. Here, we use an 11-year series on biofouling fauna from OWFs installed in Belgian waters to determine succession patterns and to unravel the role of biological interactions in shaping community development. Our analysis shows that biological interactions, besides age and location, affect diversity patterns in OWFs. The abundance of foundation species, predators, and space occupiers was significantly related to richness and/or diversity. The trends in richness, diversity, and community composition suggest that no permanent stable climax is reached after 11 years, which can be linked to the dynamic and disturbance-prone environment of offshore fouling communities.
The growing development of offshore wind energy installations across the North Sea is producing new hard anthropogenic structures in the natural soft sediments, causing changes to the surrounding ...macrobenthos. The extent of modification in permeable sediments around a gravity based wind turbine in the Belgian part of the North Sea was investigated in the period 2011 – 2012, along four gradients (south-west, north-east, south-east, north-west). Sediment grain size significantly reduced from 427 μm at 200 m to 312 ± 3 μm at 15 m from the foundation along the south-west and north-west gradients. The organic matter content increased from 0.4 ± 0.01% at 100 m to 2.5 ± 0.9% at 15 m from the foundation. The observed changes in environmental characteristics triggered an increase in the macrobenthic density from 1390 ± 129 ind m−2 at 200 m to 18 583 ± 6713 ind m−2 at 15 m together with an enhanced diversity from 10 ± 2 at 200 m to 30 ± 5 species per sample at 15 m. Shifts in species dominance were also detected with a greater dominance of the ecosystem-engineer Lanice conchilega (16–25%) close to the foundation. This study suggests a viable prediction of the effects offshore wind farms could create to the naturally occurring macrobenthos on a large-scale.
Display omitted
•Enrichment of the macrobenthic assemblages close to an offshore wind turbine.•Shift to a young and heterogenic species community.•Increase in abundance of the ecosystem-engineer Lanice conchilega.•A high spatial variability of environmental and biotic variables was observed.
•Functional impact of sand extraction, dredge disposal and offshore wind farms.•FRic and RaoQ are appropriate indices to evaluate impact of human activities.•Fuzzy correspondence analysis is a useful ...tool to visualize functional shifts.•Functional trait responses depend on degree of impact and habitat characteristics.
There is an increasing awareness that knowledge of the functional diversity of a community is key to understand how the community responds to environmental and anthropogenic pressures. The Belgian Part of the North Sea (BPNS) represents a highly dynamic area that is subject to a variety of human activities. The main objective of this study is to investigate the usefulness of functional diversity indices and fuzzy correspondence analysis (FCA) to evaluate their applicability in assessing changes in benthic functional properties in the frame of environmental impact assessments (EIAs) for dredge disposal, sand extraction and offshore wind energy exploitation. Ten traits were selected, subdivided in 47 modalities, including both response- and effect traits. Functional diversity was quantified through different functional indices while shifts in trait composition due to anthropogenic pressure were determined by FCA. The analyses were based on a benthic dataset of 1262 samples.
Results revealed that under chronic pressure of high disposal or sand extraction, the functional diversity indices – especially functional richness - showed a clear response. However, considerable variation (decrease/increase) was found for the index values between the impacted sites. Within the offshore wind farms, findings for the functional diversity indices were less pronounced. The FCA graphs revealed a shift in trait composition in all cases except for Macoma balthica and Nephtys cirrosa habitat in the dredge disposal case.
The BPNS - with different types of pressure and levels of impact - provided the ideal platform to assess the potential of biological trait-based indicators. While responses are complex and dependent on several aspects such as local habitat, pressure type or level of impact, our results proved that functional trait analyses are a necessary and complementary tool in future environmental impact assessments.
The marine benthic nitrogen cycle is affected by both the presence and activity of macrofauna and the diversity of N-cycling microbes. However, integrated research simultaneously investigating ...macrofauna, microbes and N-cycling is lacking. We investigated spatio-temporal patterns in microbial community composition and diversity, macrofaunal abundance and their sediment reworking activity, and N-cycling in seven subtidal stations in the Southern North Sea.
Our results indicated that bacteria (total and β-AOB) showed more spatio-temporal variation than archaea (total and AOA) as sedimentation of organic matter and the subsequent changes in the environment had a stronger impact on their community composition and diversity indices in our study area. However, spatio-temporal patterns of total bacterial and β-AOB communities were different and related to the availability of ammonium for the autotrophic β-AOB. Highest bacterial richness and diversity were observed in June at the timing of the phytoplankton bloom deposition, while richness of β-AOB as well as AOA peaked in September. Total archaeal community showed no temporal variation in diversity indices.
Distance based linear models revealed that, independent from the effect of grain size and the quality and quantity of sediment organic matter, nitrification and N-mineralization were affected by respectively the diversity of metabolically active β-AOB and AOA, and the total bacteria, near the sediment-water interface. Separate models demonstrated a significant and independent effect of macrofaunal activities on community composition and richness of total bacteria, and diversity indices of metabolically active AOA. Diversity of β-AOB was significantly affected by macrofaunal abundance. Our results support the link between microbial biodiversity and ecosystem functioning in marine sediments, and provided broad correlative support for the hypothesis that this relationship is modulated by macrofaunal activity. We hypothesized that the latter effect can be explained by their bioturbating and bio-irrigating activities, increasing the spatial complexity of the biogeochemical environment.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The presence of large densities of the piston-pumping polychaete Lanice conchilega can have important consequences for the functioning of marine sediments. It is considered both an allogenic and an ...autogenic ecosystem engineer, affecting spatial and temporal biogeochemical gradients (oxygen concentrations, oxygen penetration depth and nutrient concentrations) and physical properties (grain size) of marine sediments, which could affect functional properties of sediment-inhabiting microbial communities. Here we investigated whether density-dependent effects of L. conchilega affected horizontal (m-scale) and vertical (cm-scale) patterns in the distribution, diversity and composition of the typical nosZ gene in the active denitrifying organisms. This gene plays a major role in N2O reduction in coastal ecosystems as the last step completing the denitrification pathway. We showed that both vertical and horizontal composition and richness of nosZ gene were indeed significantly affected when large densities of the bio-irrigator were present. This could be directly related to allogenic ecosystem engineering effects on the environment, reflected in increased oxygen penetration depth and oxygen concentrations in the upper cm of the sediment in high densities of L. conchilega. A higher diversity (Shannon diversity and inverse Simpson) of nosZ observed in patches with high L. conchilega densities (3,185-3,440 ind. m-2) at deeper sediment layers could suggest a downward transport of NO3- to deeper layers resulting from bio-irrigation as well. Hence, our results show the effect of L. conchilega bio-irrigation activity on denitrifying organisms in L. conchilega reefs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Oxygen is recognized as a structuring factor of metazoan communities in marine sediments. The importance of oxygen as a controlling factor on meiofauna (32 µm-1 mm in size) respiration rates is ...however less clear. Typically, respiration rates are measured under oxic conditions, after which these rates are used in food web studies to quantify the role of meiofauna in sediment carbon turnover. Sediment oxygen concentration (O(2)) is generally far from saturated, implying that (1) current estimates of the role of meiofauna in carbon cycling may be biased and (2) meiofaunal organisms need strategies to survive in oxygen-stressed environments. Two main survival strategies are often hypothesized: 1) frequent migration to oxic layers and 2) morphological adaptation. To evaluate these hypotheses, we (1) used a model of oxygen turnover in the meiofauna body as a function of ambient O(2), and (2) performed respiration measurements at a range of O(2) conditions. The oxygen turnover model predicts a tight coupling between ambient O(2) and meiofauna body O(2) with oxygen within the body being consumed in seconds. This fast turnover favors long and slender organisms in sediments with low ambient O(2) but even then frequent migration between suboxic and oxic layers is for most organisms not a viable strategy to alleviate oxygen limitation. Respiration rates of all measured meiofauna organisms slowed down in response to decreasing ambient O(2), with Nematoda displaying the highest metabolic sensitivity for declining O(2) followed by Foraminifera and juvenile Gastropoda. Ostracoda showed a behavioral stress response when ambient O(2) reached a critical level. Reduced respiration at low ambient O(2) implies that meiofauna in natural, i.e. suboxic, sediments must have a lower metabolism than inferred from earlier respiration rates conducted under oxic conditions. The implications of these findings are discussed for the contribution of meiofauna to carbon cycling in marine sediments.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Marine aggregates have been intensively extracted in the North-East Atlantic over the past decades. This study aimed to assess the effect of sand extraction on benthic ecosystem functioning using a ...combination of biological traits and functional indices (the bioturbation (BP
c
) and irrigation potential (IP
c
) and secondary production (SP
c
) of the macrobenthic community). Data on macrobenthos, sediment properties and extraction intensity were collected over a time period of ten years (2010 – 2019) for three coarse sediment extraction areas in the Belgian Part of the North Sea, each with a different extraction regime. Sediment parameters such as the medium sand fraction (250 – 500 µm) and median grain size showed a significant effect on all functional indices. Whilst sand extraction variables only significantly affected secondary production estimates. The secondary production of the macrobenthic community decreased following a high yearly extraction intensity, whereas a high cumulative (10-year period) extraction intensity resulted in a slightly increased secondary production. Species-specific responses revealed that these high cumulative extraction volumes increased the abundance of opportunistic species, which could have contributed to the higher SP
c
values observed in cumulative disturbed areas. Response traits such as tube-living and sessile individuals with a pelagic egg development were positively influenced by a long-term disturbance, an indication of a more disturbance-tolerant community. A short-term disturbance rather seemed to favor a macrobenthic community characterized by a higher burrowing capability. In terms of effect traits, both short- and long-term extraction clearly favored deposit feeders, which can structure organic matter distribution and thus indirectly influence nutrient and oxygen fluxes as well. Future
in situ
measurements in sand extraction areas could help to unravel and strengthen our understanding of the ecosystem processes linked to these trait-based observations.
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