Enhancing ecological integrity while preserving ecosystem services: Constructing soft‐sediment islands in a shallow lake

Human society strongly depends on vital functions and services of natural ecosystems (IPBES, 2019; Zedler & Kercher, 2005). These include food production, fisheries, recreation, drinking water supply, energy generation carbon storage (Clarkson et al., 2013; Consequently, do not only have intrinsic cultural values but are increasingly requested to provide multiple simultaneously, including economic returns. This can lead ecosystem degradation by overexploitation, pollution habitat loss (Davidson, 2014; WWF, 2020). Many the world's freshwater lakes, estuaries wetlands important for humans, also scarce, used competed (Reynaud Lanzanova, 2017; Schallenberg 2013). Worldwide, many aquatic influenced engineering a specific, single service (e.g. damming river generate hydropower) that impair its ecological integrity. Engineering often homogenizes abiotic biotic conditions, inhibits dynamics such as water-level fluctuations leads reductions in biodiversity, trophic complexity functional diversity at each level (Gibbs, 2000; Millennium Ecosystem Assessment, currently need sustainable nature development strategies, because their integrity has eroded result wide range simultaneous demands associated modifications 2014). Classical restoration ecosystems, which large degree focused returning degraded pre-human-use is challenging (Higgs Higgs 2018). lakes modified flood protection, reservoirs or fulfil new, desired, recreation With classical restoration, where past undone, least some these new humans unavoidably lost Furthermore, projects affect (part of) desired mostly face complicated, long-term negotiations (Perring 2015; Suding 2015) – about what should be historical reference state return To overcome challenges, novel strategies degrading needed enhance integrity, while preserving socio-economic benefits (Corlett, 2016; Gulati 2008; 2018; Martin, 2017). Here we present forward-looking approach shallow lake Markermeer centre Netherlands, like world human-created (Hogeboom The was formed construction two dikes land reclamations marine estuary, named Zuiderzee (Figure 1a 1b). First, 32-km long dike (named Afsluitdijk) completed 1932, turned main tidal estuary IJssel into 357,000-ha over time. IJsselmeer, still fed with fresh IJssel, experienced drastic change salinity, web composition hydrology (Cremer 2009). Second, reclamation occurred 1942 (60,000 ha) between 1955 1968 (114,000 ha). Third, 27-km Houtribdijk) 1975 divided IJsselmeer lakes: almost land-locked (70,000 southwest limited riverine input (river Eem, discharge 10 m3 s−1), drainage (113,000 northeast (discharge 340 s−1; Figure 1b; Vijverberg 2011; terminology sensu Heino 2021). Both developed distinct started fishing supply agriculture (Gulati van Donk, 2002). However, activities did automatically introduce elements gradual land–water transitions, heterogeneity depths one would expect well-functioning lowland processes (Schindler Scheuerell, initially towards piscivorous benthic feeding waterbirds. Benthivorous waterbirds common pochard Aythya ferina, tufted duck A. fuligula greater scaup marila profited from establishing populations non-native mussels zebra mussel Dreissena polymorpha quagga D. rostriformis. Piscivorous great crested grebe Podiceps cristatus, smew Mergellus albellus merganser Mergus thriving rich stock fish smelt Osmerus eperlanus source (Noordhuis, last decades, particularly been declining (Lammens Noordhuis, Compared 1980s, numbers benthivorous bird species halved, coinciding decrease population one-tenth biomass (de Graaf Keller, 2010; decreases higher levels were likely caused factors, an increase turbidity primary productivity der Velde Riel 2019). resulted long-standing societal wish nature-based solution this problem, is, addressing challenge working enhancing (Seddon goal improve lake's adding structure more typical low altitudes (Heino 2021), without compromising it provides 2008). ecologically impossible, marine, after damming, different no true condition. by, example, removing socio-economically undesired due current (flood storage, fisheries) Therefore, Dutch Society Nature Conservation (‘Natuurmonumenten’), cooperation provincial national authorities, proposed innovative large-scale solution. It follows rewilding restoring much possible, whereas uses achieve this. encompasses building 700-ha archipelago consisting five islands ‘Marker Wadden’ 2016 2020. concept first results Marker Wadden project, ambitious, project Netherlands aimed improving maintaining services. reverse decline Markermeer's aims bottom-up via solutions. therefore, targets three factors missing comparison thought limit production 2). historically highly productive, nutrient-rich coastal system inputs 2a). Nutrient sustain column lake, closing off most retention available nutrients iron-rich sediment. sediment consists Pleistocene sands covered 5–8-m layer Holocene clays, silts fine (Troelstra 2018), turn floating mud 2b). 0.1–0.2 m upper fraction maximum settling velocity < 0.01 mm s−1 slightly coarser 0.5 4.0 s−1, easily resuspended wind speeds 4 (Vijverberg 2011). While able sink deeper areas larger enclosed >25-km fetch length now suffers continuous resuspension material Lake essentially became similar (Figures 1b), leading suspended concentrations 50 mg L−1 near surface increasing well 100 case very strong winds (van Kessel Fine reduces light availability may hamper zooplankton feeding, thereby limiting transfer efficiency phytoplankton de Lucas Pardo G.-Tóth Penning basalt asphalt form homogeneous steep, hard shorelines stable, managed, reversed (maximum variation 0.5–1.0 m, high summer winter). offers space relying transitions littoral zone reproduction fish, nutrient cycling influx terrestrial sources (Benson Magnuson, 1992; McGoff mitigate negative effects aforementioned constructing add connections, shelter, waters 1 2c). constructions aim previously types 2021; Schindler 2002) lake. stone sand dunes windward side (west) shelter subsequent constructions. On leeward structures, constructed itself. ring made sands, extracted bottom ranging 8 35 deep. within subsequently predominantly filled above clays top 5–8 Subsidence below (Temmink 2021) marshlands (<1 m), partly reconnected end ∼0.5 2 deep plus excavations possible own value procedure itself removed sediments sheltered expected further stimulate sediments. created series lacking Markermeer. connections hypothesized runoff water. develop productive availability, quick warming spring, wind, silts. Hence, increase, longer hampered limitation (Schallenberg establishment submerged macrophyte- shoreline-vegetation could help trapping solids (Barko James, 1998). combined positively stimulation providing all web. vision behind induce conditions foraging spawning breeding recreational function largest newly therefore accessible general public, other remain closed public (Natuurmonumenten, island, small settlement 1c). built off-grid using exclusively materials includes harbour, holiday houses visitor centre. Moreover, they group accommodation field station educational research purposes, run ferry enable recreationists visit offer guided tours, educate nature. dedicated regular communication involvement volunteers during aspects ensure acceptance. deliberately integrates education, innovation Our observations implications even though under suggest quickly profit habitats (for timeline, see 3). reduction followed proven difficult assess early phase part themselves. included creation basins 3–4 ha (late Each basin surrounded sheltering separating rest otherwise leaving identical open As proof how web, surveyed years (on 24 May 2019) comparing locations close just Wadden. At basins, examined assessing (1) total chlorophyll-a samples PHYTO-PAM analyser (Heinz Walz 91090 GmbH, Effeltrich, Germany), sum blue, green brown channels indication (μg L−1); (2) densities concentrating 30 L through 80-μm net 50-mL tube fixating lugol's iodine, counting LEICA M125C stereo microscope; (3) macrophyte presence dragging 30-cm rake four times across sediment, washing drying collected 60°C 48 h, weighing dried nearest 0.1 g; (4) sampling macrofauna grabbing 15 × cm sample 10-cm bottom, estimating dry weight based identifications known length-biomass relationships. affected webs 3 years. Basin moved phytoplankton-dominated state, community Copepoda Annelida 4). Basins clearer 4b), lower Cladocera visible naked eye 4d). In 4f), dominated Arthropoda Mollusca instead Chironomid larvae, snails locally opossum shrimps Neomysis sp. 4h). Although differently, merely creating potential relations observation macrophytes colonize among confirmed larger-scale survey Underwater vegetation mapped islands, revealed eight Charophyte species. Dominant sago pondweed Potamogeton pectinatus, horned Zannichellia palustris, stonewort Chara vulgaris starry Nitellopsis obtuse (Scirpus Ecologisch Advies, Before started, rarely eastern (Vonk 2019), clay soil type less suitable (Van Zuidam Peeters, 2015). marshlands, transition zones growing season. year, marsh fleawort Tephroseris palustris dominant species, probably wind-dispersed, pioneering plant establish Willows Salix colonized drier marshland zones. helophyte marshes rather than wet forests. willows actively germination prevented management until 2020, rhizomes reed Phragmites australis broadleaf cattail Typha latifolia sown protected against herbivores grazing pressure systems (Bakker 2016). Protection avian (notably greylag geese Anser anser) rapid Rijk Dulfer, Surveys assessments fishes birds. Fish 2018 2019, finding 19 larval several types. native roach Rutilus rutilus, European perch Perca fluviatilis Eurasian ruffe Gymnocephalus cernua, typically Gobidae found (Emmerik, 2018, Numerous use extensively monitored. Over 20,000 martins Riparia riparia, 3000 northern shovelers Spatula clypeata, 1000 pied avocets Recurvirostra avosetta, black terns Chlidonias niger hundreds little gulls Hydrocoloeus minutus For shovelers, Sterna hirundo harboured, respectively, > 6%, 2% flyway given moment 2019 Winden, ringed plover Charadrius hiaticula terns, 10% attracted habitat. observed had and/or breed decades Netherlands. Rarer flamingos Phoenicopterus roseus spoonbills Platalea leucorodia encountered, nests gull-billed Gelochelidon nilotica long-tailed ducks Clangula hyemalis decades. Overall, seems layers shift way simplistic structurally complex allows coexistence wider conditions. Natural taking advantage increased heterogeneity, temperate lakes. Even former estuarine return, developing might resilience future perturbations (Carpenter Cottingham, 1997; Scheffer 2001). Whether sufficient downward trend completely remains determined. twenty-first century requires solutions thus views nature, sustainability, resilience, forms development. Initiatives human-impacted slowed down stopped resistance give up existing derived lack developed. Here, perspective situation impossible historic reference, adherence (novel) benefits. since start trends positive. There signs fisheries negatively affected. respect opened September welcomed 20 000 visitors, 180 charter vessels ships overnight stay harbour year featured 150 regional news, 250 too affects provides, responses outline here hopefully inspire scientists practitioners design initiate collide multifunctionality. designed dual function, aiming facilitate human ecosystem. illustrated study, thinking pave ways human-made counteract globally. If chance, capacity maintain societies. authors thank Natuurmonumenten support, Gieskes Strijbis Fonds funding Jani constructive comments. co-authors RP AB work non-profit conservation organization responsible (Natuurmonumenten). We declare conflicts interest. LB, HO CL initiated writing HJ contributed data. After discussions interpretation, RT wrote draft manuscript. All final paper. peer review history article https://publons.com/publon/10.1002/2688-8319.12098. Data Dryad Digital Repository: https://doi.org/10.5061/dryad.2v6wwpznx Leeuwen