Initiating and upscaling mussel reef establishment with life cycle informed restoration:Successes and future challenges

Worldwide, coastal ecosystems are rapidly degrading in quality and extent. While novel restoration designs include facilitation to enhance restoration success in stressful environments, they typically focus on a single life-stage, even though many organisms go through multiple life-stages accompanied by different bottlenecks. A new approach – life cycle informed restoration – was designed to ameliorate multiple bottlenecks throughout an organism's life cycle. It has successfully been tested on a small scale to facilitate intertidal bivalve reef formation in the Netherlands and Florida. Yet, it remains unknown whether this approach can be scaled to ecosystem-relevant scales. To test whether life cycle informed restoration is upscalable, we conducted a large-scale restoration experiment using blue mussel reefs as a model system. In our experiment, we used biodegradable structures to temporarily facilitate mussel reef formation by providing early-life settlement substrates, and subsequently, reduce post-settlement predation on an intertidal flat in the Wadden Sea, the Netherlands. The structures were placed in 10 × 20 m plots, mimicking bands found in natural mussel beds, spread out across 650 m, and were followed for two years. Our results show that the structures enhance mussel biomass (0.7 ± 0.2 kg DW m−2), as mussels were absent in bare plots. However, biomass varied within plots; in intact structures it was 60 times higher (1.2 ± 0.2 kg DW m−2) than in those that became buried (0.02 ± 0.009 kg DW m−2). Next to burial, 18–46% of the structures were lost due to technical failure, especially during winters at this exposed site. We show that the life cycle informed restoration principle works, but we encountered technical challenges due to larger scale processes (e.g. sedimentation). Furthermore, environmental information is essential for site selection, and for restoration, the functioning of such structures should be tested under extreme conditions before upscaling

Actions of PACAP and VIP on melanotrope cells of Xenopus laevis

Item does not contain fulltextThe neuropeptides, pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) are implicated in the regulation of gene expression and hormone secretion in mammalian melanotrope cells and a mammalian pro-opiomelanocortin (POMC)-producing tumor cell line, but the physiological relevance of this regulation is elusive. The purpose of the present study was to establish if these peptides affect biosynthetic and secretory processes in a well-established physiological model for endocrine cell functioning, the pituitary melanotrope cells of the amphibian Xenopus laevis, which hormonally control the process of skin color adaptation to background illumination. We show that both PACAP and VIP are capable of stimulating the secretory process of the Xenopus melanotrope cell. As the peptides are equipotent, they may exert their actions via a VPAC receptor. Moreover, PACAP stimulated POMC biosynthesis and POMC gene expression. Strong anti-PACAP immunoreactivity was found in the pituitary pars nervosa (PN), suggesting that this neurohemal organ is a source of neurohormonal PACAP action on the melanotropes in the intermediate pituitary. We propose that the PACAP/VIP family of peptides has a physiological function in regulating Xenopus melanotrope cell activity during the process of skin color adaptation

Overcoming establishment thresholds for peat mosses in human-made bog pools

Globally, peatlands have been affected by drainage and peat extraction, with adverse effects on their functioning and services. To restore peat-forming vegetation, drained bogs are being rewetted on a large scale. Although this practice results in higher groundwater levels, unfortunately it often creates deep lakes in parts where peat was extracted to greater depths than the surroundings. Revegetation of these deeper waters by peat mosses appears to be challenging due to strong abiotic feedbacks that keep these systems in an undesired bare state. In this study, we theoretically explore if a floating peat mat and an open human-made bog lake can be considered two alternative stable states using a simple model, and experimentally test in the field whether stable states are present, and whether a state shift can be accomplished using floating biodegradable structures that mimic buoyant peat. We transplanted two peat moss species into these structures (pioneer sp. Sphagnum cuspidatum and later-successional sp. S. palustre) with and without additional organic substrate. Our model suggests that these open human-made bog lakes and floating peat mats can indeed be regarded as alternative stable states. Natural recovery by spontaneous peat moss growth, i.e., a state shift from open water to floating mats, is only possible when the water table is sufficiently shallow to avoid light limitation (<0.29 m at our site). Our experiment revealed that alternative stable states are present and that the floating structures facilitated the growth of pioneer S. cuspidatum and vascular plants. Organic substrate addition particularly facilitated vascular plant growth, which correlated to higher moss height. The structures remained too wet for the late-successional species S. palustre. We conclude that open water and floating peat mats in human-made bog lakes can be considered two alternative stable states, and that temporary floating establishment structures can induce a state shift from the open water state to peat-forming vegetation state. These findings imply that for successful restoration, there is a clear water depth threshold to enable peat moss growth and there is no need for addition of large amounts of donor-peat substrate. Correct species selection for restoration is crucial for success

Nature development in degraded landscapes: How pioneer bioturbators and water level control soil subsidence, nutrient chemistry and greenhouse gas emission

The restoration of degraded ecosystems and landscapes is challenging, because returning to the original state is often socio-economically unfeasible. A novel approach is to construct new ecosystems to improve the functioning of degraded landscapes. However, the development of novel ecosystems is largely driven by the pre-construction hydrogeophysical and ecological conditions of the soil. In Lake Markermeer, a deteriorating freshwater lake in the Netherlands, a large archipelago is currently being constructed to boost the ecological functioning of the lake. Hence, islands – with wetlands and with more elevated and dryer areas – have been created to sustain biodiversity and key biogeochemical functions such as nutrient cycling. The islands are constructed from lake-bottom sediments. To study how two potentially important drivers, water level and bioturbation, affect soil characteristics in a novel wetland ecosystem, we experimentally tested the effects of water level (-30, -10 and 5 cm), and bioturbation by earthworms (Lumbricus rubellus) and Tubifex spp. in a microcosm experiment. We demonstrate that a high water level prevents soil subsidence, soil crack formation and carbon dioxide (CO2) emissions, and affects nitrogen cycling. In dryer soils, the presence of earthworms strongly increases CO2 emissions next to reducing soil crack formation, while Tubifex spp. in wetter soils hardly affect soil characteristics. Our findings highlight the important roles of both water level and bioturbation for the functioning of novel soils, which likely affects vegetation development in novel ecosystems. This knowledge can be used to aid the construction and nature development of novel wetlands

Nature development in degraded landscapes: How pioneer bioturbators and water level control soil subsidence, nutrient chemistry and greenhouse gas emission

The restoration of degraded ecosystems and landscapes is challenging, because returning to the original state is often socio-economically unfeasible. A novel approach is to construct new ecosystems to improve the functioning of degraded landscapes. However, the development of novel ecosystems is largely driven by the pre-construction hydrogeophysical and ecological conditions of the soil. In Lake Markermeer, a deteriorating freshwater lake in the Netherlands, a large archipelago is currently being constructed to boost the ecological functioning of the lake. Hence, islands – with wetlands and with more elevated and dryer areas – have been created to sustain biodiversity and key biogeochemical functions such as nutrient cycling. The islands are constructed from lake-bottom sediments. To study how two potentially important drivers, water level and bioturbation, affect soil characteristics in a novel wetland ecosystem, we experimentally tested the effects of water level (-30, -10 and 5 cm), and bioturbation by earthworms (Lumbricus rubellus) and Tubifex spp. in a microcosm experiment. We demonstrate that a high water level prevents soil subsidence, soil crack formation and carbon dioxide (CO2) emissions, and affects nitrogen cycling. In dryer soils, the presence of earthworms strongly increases CO2 emissions next to reducing soil crack formation, while Tubifex spp. in wetter soils hardly affect soil characteristics. Our findings highlight the important roles of both water level and bioturbation for the functioning of novel soils, which likely affects vegetation development in novel ecosystems. This knowledge can be used to aid the construction and nature development of novel wetlands

Initiating and upscaling mussel reef establishment with life cycle informed restoration: Successes and future challenges

Worldwide, coastal ecosystems are rapidly degrading in quality and extent. While novel restoration designs include facilitation to enhance restoration success in stressful environments, they typically focus on a single life-stage, even though many organisms go through multiple life-stages accompanied by different bottlenecks. A new approach – life cycle informed restoration – was designed to ameliorate multiple bottlenecks throughout an organism's life cycle. It has successfully been tested on a small scale to facilitate intertidal bivalve reef formation in the Netherlands and Florida. Yet, it remains unknown whether this approach can be scaled to ecosystem-relevant scales. To test whether life cycle informed restoration is upscalable, we conducted a large-scale restoration experiment using blue mussel reefs as a model system. In our experiment, we used biodegradable structures to temporarily facilitate mussel reef formation by providing early-life settlement substrates, and subsequently, reduce post-settlement predation on an intertidal flat in the Wadden Sea, the Netherlands. The structures were placed in 10 × 20 m plots, mimicking bands found in natural mussel beds, spread out across 650 m, and were followed for two years. Our results show that the structures enhance mussel biomass (0.7 ± 0.2 kg DW m−2), as mussels were absent in bare plots. However, biomass varied within plots; in intact structures it was 60 times higher (1.2 ± 0.2 kg DW m−2) than in those that became buried (0.02 ± 0.009 kg DW m−2). Next to burial, 18–46% of the structures were lost due to technical failure, especially during winters at this exposed site. We show that the life cycle informed restoration principle works, but we encountered technical challenges due to larger scale processes (e.g. sedimentation). Furthermore, environmental information is essential for site selection, and for restoration, the functioning of such structures should be tested under extreme conditions before upscaling

Initiating and upscaling mussel reef establishment with life cycle informed restoration: Successes and future challenges

Worldwide, coastal ecosystems are rapidly degrading in quality and extent. While novel restoration designs include facilitation to enhance restoration success in stressful environments, they typically focus on a single life-stage, even though many organisms go through multiple life-stages accompanied by different bottlenecks. A new approach – life cycle informed restoration – was designed to ameliorate multiple bottlenecks throughout an organism's life cycle. It has successfully been tested on a small scale to facilitate intertidal bivalve reef formation in the Netherlands and Florida. Yet, it remains unknown whether this approach can be scaled to ecosystem-relevant scales. To test whether life cycle informed restoration is upscalable, we conducted a large-scale restoration experiment using blue mussel reefs as a model system. In our experiment, we used biodegradable structures to temporarily facilitate mussel reef formation by providing early-life settlement substrates, and subsequently, reduce post-settlement predation on an intertidal flat in the Wadden Sea, the Netherlands. The structures were placed in 10 × 20 m plots, mimicking bands found in natural mussel beds, spread out across 650 m, and were followed for two years. Our results show that the structures enhance mussel biomass (0.7 ± 0.2 kg DW m−2), as mussels were absent in bare plots. However, biomass varied within plots; in intact structures it was 60 times higher (1.2 ± 0.2 kg DW m−2) than in those that became buried (0.02 ± 0.009 kg DW m−2). Next to burial, 18–46% of the structures were lost due to technical failure, especially during winters at this exposed site. We show that the life cycle informed restoration principle works, but we encountered technical challenges due to larger scale processes (e.g. sedimentation). Furthermore, environmental information is essential for site selection, and for restoration, the functioning of such structures should be tested under extreme conditions before upscaling

Biodegradable artificial reefs enhance food web complexity and biodiversity in an intertidal soft-sediment ecosystem

Reef-forming species form integral aspects of coastal ecosystems, but are rapidly degrading world-wide. To mitigate these declines, nature managers increasingly rely on the restoration of habitat-structuring, reef-forming species by, for example, introducing artificial reefs that may directly function as complex reef habitat. Since the use of biodegradable structures to restore biogenic reefs is becoming a popular technique, its effectiveness as reef habitat must be assessed. Therefore, we examine the trophic complexity on experimental large-scale biodegradable artificial reefs using food web network analysis. We placed biodegradable artificial reefs on soft-sediment intertidal flats in the Dutch Wadden Sea in a large-scale (~650 m) and 2.5-year-long experiment. We compared food web networks and biodiversity indicators between biodegradable reefs and bare controls and quantified species composition inside and near the artificial reef community to assess the expansion of the reef community. During 2.5 years, we observed that artificial reefs changed food web networks compared to bare controls: in species richness (+76%), link density (the number of interactions per species; +15%) and the fraction of basal species (species of lowest trophic level; +40%), but lowered the connectance: the realized fraction of all possible links between species (−33%). Their effects on food web networks increased over time with a higher species richness (+22%) and more complex food web (link density +13%) on the artificial reef 2.5 years after deployment compared to 1.5 years. However, the effects of the reefs did not extend beyond the reef structures; the species composition and biodiversity of macrozoobenthos near the reefs were comparable to the control. Synthesis and applications. This study shows that biodegradable artificial reefs offer an effective tool for the restoration of food web complexity and biodiversity of intertidal soft-sediment systems. However, application needs to be carefully considered as the reef-building species did not expand beyond our structures, despite the ambitious spatial extent of this experiment. Therefore, we recommend restoration practitioners to design artificial reefs in such a way that they generate ecosystem connectivity (facilitation of higher trophic levels) and biogeomorphological effects on a landscape scale (reef expansion beyond the structures)

Biodegradable artificial reefs enhance food web complexity and biodiversity in an intertidal soft-sediment ecosystem

Reef-forming species form integral aspects of coastal ecosystems, but are rapidly degrading world-wide. To mitigate these declines, nature managers increasingly rely on the restoration of habitat-structuring, reef-forming species by, for example, introducing artificial reefs that may directly function as complex reef habitat. Since the use of biodegradable structures to restore biogenic reefs is becoming a popular technique, its effectiveness as reef habitat must be assessed. Therefore, we examine the trophic complexity on experimental large-scale biodegradable artificial reefs using food web network analysis. We placed biodegradable artificial reefs on soft-sediment intertidal flats in the Dutch Wadden Sea in a large-scale (~650 m) and 2.5-year-long experiment. We compared food web networks and biodiversity indicators between biodegradable reefs and bare controls and quantified species composition inside and near the artificial reef community to assess the expansion of the reef community. During 2.5 years, we observed that artificial reefs changed food web networks compared to bare controls: in species richness (+76%), link density (the number of interactions per species; +15%) and the fraction of basal species (species of lowest trophic level; +40%), but lowered the connectance: the realized fraction of all possible links between species (−33%). Their effects on food web networks increased over time with a higher species richness (+22%) and more complex food web (link density +13%) on the artificial reef 2.5 years after deployment compared to 1.5 years. However, the effects of the reefs did not extend beyond the reef structures; the species composition and biodiversity of macrozoobenthos near the reefs were comparable to the control. Synthesis and applications. This study shows that biodegradable artificial reefs offer an effective tool for the restoration of food web complexity and biodiversity of intertidal soft-sediment systems. However, application needs to be carefully considered as the reef-building species did not expand beyond our structures, despite the ambitious spatial extent of this experiment. Therefore, we recommend restoration practitioners to design artificial reefs in such a way that they generate ecosystem connectivity (facilitation of higher trophic levels) and biogeomorphological effects on a landscape scale (reef expansion beyond the structures)