1 INTRODUCTION

Ecological processes in shallow aquatic ecosystems can be strongly impacted by wind (Janatian et al., 2020; Stockwell et al., 2020). Wind can directly affect the base of the aquatic food web: the primary producers including macrophytes, benthic algae and phytoplankton. For example, macrophyte establishment may be inhibited directly because of stem breakage, uprooting, or limitations in establishment of their propagules (Jupp & Spence, 1977; Keddy, 1983; Schutten et al., 2005; Van Zuidam & Peeters, 2015). In addition, benthic algae may be unable to colonise exposed habitat as a result of sediment resuspension and instable sediment (Jorge & Beusekom, 1995). As such, wind-induced disturbances may favour phytoplankton dominance by releasing it from otherwise high competition by other primary producers (Hansson et al., 2020; Sand-Jensen & Borum, 1991). Beyond direct wind effects, wind also has indirect effects on shallow lake ecosystem functioning. A key indirect effect of wind in shallow lakes is its effect on sediment resuspension, which can alter relative resource availabilities for distinct primary producers (Tammeorg et al., 2013). For example, sediment resuspension typically leads to higher nutrient concentrations in the water column coupled with decreased light availability (Blottière et al., 2017; Tang et al., 2020). Consequently, high nutrient availability in the water facilitates the growth of phytoplankton, whereas low light availability created by high phytoplankton abundance and suspended sediments inhibits or restricts the growth of submerged macrophytes or benthic algae (Jäger & Diehl, 2014).

Wind-induced turbulence also can affect secondary producers in shallow aquatic ecosystems. Wind can modify the community of secondary producers (zooplankton) directly (Ohman & Romagnan, 2016; Zhou et al., 2016) as well as indirectly by affecting the quantity and quality of their food (phytoplankton) (Cyr & Coman, 2012; Durham et al., 2013; Tang et al., 2020). Direct effects are, for example, that wind-induced turbulence may inhibit the growth of large-sized zooplankton species when their body size exceeds the Kolmogorov length scale as they are more affected by eddy motion (Peters & Marrasé, 2000). Specifically, organisms larger than the diameter of the smallest turbulent eddy are directly affected by the turbulent shear forces, which may impair food detection or capture, or directly lead to body damage (G.-Tóth et al., 2011; Visser et al., 2009; Zhou et al., 2016). Although the sediment resuspension process tends to increase phytoplankton biomass (Carrick et al., 1993; Kang et al., 2019), higher inorganic suspended solid concentrations in the water column following this process may pose an indirect constraint on herbivore (zooplankton) feeding, because suspended solids can mechanically interfere with food intake or dilute gut content (Kirk & Gilbert, 1990; Koenings et al., 1990). As a result, wind-induced turbulence potentially may lower the trophic transfer efficiency between phytoplankton and zooplankton – defined as the total production ratio between adjacent trophic levels (Lindeman, 1942) – as a consequence of the dominance of small-sized zooplankton with relatively lower grazing capability and the high suspended solids concentrations (Hall et al., 1976). The decreased trophic transfer efficiency between phytoplankton and zooplankton subsequently might lead to the decline of higher trophic production (Barneche et al., 2021; Kazama et al., 2021).

Shallow lakes may be characterised by two alternative stable states: an aquatic vegetation-dominated clear water state and a phytoplankton-dominated turbid water state (Hargeby et al., 2004; Janssen et al., 2014; Scheffer et al., 1993). Wind-induced turbulence, for example, may maintain the phytoplankton-dominated turbid state by directly favouring phytoplankton to be the dominant primary producer (Blottière et al., 2017; Tang et al., 2020), while indirectly decreasing trophic transfer efficiency between phytoplankton and zooplankton (G.-Tóth et al., 2011; Hall et al., 1976; Zhou et al., 2016). Reducing wind-induced turbulence therefore may be a suitable method to shift a phytoplankton-dominated turbid water state to an aquatic vegetation-dominated clear-water state, thereby stimulating higher trophic production in shallow lakes. However, the complex effects of wind make it difficult to predict the response of aquatic food webs to sheltered conditions. Suspended sediment increases nutrient availability in the water column (i.e., under exposed conditions), and therefore phytoplankton biomass is expected to be lower under sheltered conditions when the sediment settles and phytoplankton growth may become nutrient-limited (Gao et al., 2021; Zhang et al., 2020). Additionally, nutrient limitation may decrease phytoplankton quality because it potentially leads to higher carbon (C):nutrient ratios in primary producers (Ågren, 2004; Sterner & Elser, 2002). Furthermore, if submerged macrophytes or benthic algae establish under sheltered conditions, these will compete with phytoplankton for nutrients (Hansson et al., 2020; Sand-Jensen & Borum, 1991), which may further strengthen nutrient limitation and decrease both phytoplankton biomass and its quality. As such, on the one hand, sheltered conditions seem favourable for larger zooplankton that can profit from easy feeding in a water column with little interference of suspended sediments (Kirk & Gilbert, 1990). However, on the other hand, they may be limited by low phytoplankton production and its quality. As a result, it is questionable whether shelter benefits higher trophic levels by improved trophic transfer efficiency leading to higher zooplankton biomass. Instead, under sheltered conditions, benthic algae and submerged macrophytes may be the dominant producers, and higher trophic levels may benefit from increased abundances of grazing benthic fauna on benthic algae mats, periphyton on macrophytes and the macrophytes themselves (Karlsson et al., 2009), rather than increased zooplankton production. In the latter case, shelter results in higher food-web complexity, offering alternative pathways to stimulate higher trophic levels rather than strengthening the phytoplankton–zooplankton food chain.

Here, we studied the effects of shelter on the relative dominance of primary producers, trophic transfer efficiency between phytoplankton and zooplankton, and benthic fauna in a 2-month in situ manipulative field experiment in shallow water in the newly constructed archipelago Marker Wadden in the Netherlands. We artificially created shelter and manipulated the presence of submerged macrophytes, which resulted in three treatments: (1) no shelter, (2) shelter and (3) shelter with macrophytes. We hypothesised that shelter would: (a) result in shifts in relative dominance of primary producers, expecting a reduction of phytoplankton biomass, and increase in biomass of benthic algae, macrophytes and periphyton; (b) enhance the trophic transfer efficiency between phytoplankton and zooplankton; and (c) increase the abundance of benthic fauna grazing on benthic algae, periphyton and macrophytes.

中文翻译：

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庇护所对初级生产者的相对优势和水生食物网中的营养转移效率的影响：对浅湖恢复的影响

1 简介

浅水生态系统中的生态过程会受到风的强烈影响（Janatian 等人，  2020 年；Stockwell 等人，  2020 年）。风可以直接影响水生食物网的基础：初级生产者包括大型植物、底栖藻类和浮游植物。例如，大型植物的建立可能会因为茎折断、连根拔起或繁殖体建立受限而受到直接抑制（Jupp & Spence,  1977 ; Keddy,  1983 ; Schutten et al.,  2005 ; Van Zuidam & Peeters,  2015）。此外，由于沉积物再悬浮和不稳定的沉积物，底栖藻类可能无法在暴露的栖息地定居（Jorge & Beusekom，  1995）。因此，风引起的干扰可能会通过将浮游植物从其他初级生产者的激烈竞争中解放出来，从而有利于浮游植物的优势（Hansson 等人，  2020 年；Sand-Jensen 和 Borum，  1991 年）。除了直接的风影响外，风还对浅湖生态系统功能产生间接影响。风在浅湖中的一个关键间接影响是它对沉积物再悬浮的影响，这可以改变不同初级生产者的相对资源可用性（Tammeorg 等人，  2013 年）。例如，沉积物再悬浮通常会导致水体中的养分浓度升高，同时光照利用率降低（Blottière 等人，  2017 年；Tang 等人，  2020 年））。因此，水中的高营养物质可促进浮游植物的生长，而由高浮游植物丰度和悬浮沉积物造成的低光照可抑制或限制沉水大型植物或底栖藻类的生长（Jäger 和 Diehl，  2014 年）。

风引起的湍流也会影响浅水生态系统中的次级生产者。风可以直接改变次级生产者（浮游动物）群落（Ohman & Romagnan,  2016 ; Zhou et al.,  2016），也可以通过影响食物的数量和质量（浮游植物）间接改变（Cyr & Coman,  2012 ; Durham等人，  2013 年；唐等人，  2020 年）。直接影响是，例如，当大型浮游动物的体型超过 Kolmogorov 长度尺度时，风引起的湍流可能会抑制它们的生长，因为它们更容易受到涡流运动的影响（Peters & Marrasé，2000）。具体而言，大于最小湍流直径的生物直接受到湍流剪切力的影响，这可能会影响食物的检测或捕获，或直接导致身体损伤（G.-Tóth 等人，  2011 年；Visser 等人。 ，  2009 年；周等人，  2016 年）。尽管沉积物再悬浮过程往往会增加浮游植物的生物量（Carrick 等人，  1993 年；Kang 等人，  2019 年），但在此过程之后水体中较高的无机悬浮固体浓度可能会对食草动物（浮游动物）的摄食造成间接限制，因为悬浮固体会机械地干扰食物摄入或稀释肠道内容（Kirk & Gilbert,  1990; Koenings 等人，  1990 年）。因此，风引起的湍流可能会降低浮游植物和浮游动物之间的营养转移效率——定义为相邻营养级之间的总产量比（林德曼，  1942 年）——这是由于小型浮游动物占优势，相对较低放牧能力和高悬浮固体浓度（Hall 等人，  1976 年）。随后，浮游植物和浮游动物之间的营养转移效率下降可能导致较高营养产量的下降（Barneche 等人，  2021 年；Kazama 等人，  2021 年）。

浅水湖泊可能具有两种可供选择的稳定状态：以水生植被为主的清水状态和以浮游植物为主的浑水状态（Hargeby et al.,  2004 ; Janssen et al.,  2014 ; Scheffer et al.,  1993）。例如，风引起的湍流可以通过直接有利于浮游植物成为主要的初级生产者来维持以浮游植物为主的混浊状态（Blottière et al.,  2017 ; Tang et al.,  2020），同时间接降低浮游植物之间的营养转移效率和浮游动物（G.-Tóth 等人，  2011 年；Hall 等人，  1976 年；Zhou 等人，  2016 年）。因此，减少风引起的湍流可能是将浮游植物为主的浑水状态转变为水生植被为主的清水状态的合适方法，从而刺激浅水湖泊中更高的营养生产。然而，风的复杂影响使得难以预测水生食物网对遮蔽条件的反应。悬浮沉积物增加了水体中养分的可用性（即在暴露条件下），因此当沉积物沉降并且浮游植物的生长可能变得养分受限时，浮游植物生物量在遮蔽条件下预计会降低（Gao et al.,  2021 ; Zhang等人，  2020）。此外，养分限制可能会降低浮游植物的质量，因为它可能导致初级生产者的碳 (C)：养分比例更高（Ågren，  2004 年；Sterner & Elser，  2002 年）。此外，如果淹没的大型植物或底栖藻类在遮蔽条件下生长，它们将与浮游植物竞争养分（Hansson 等，  2020；Sand-Jensen & Borum，  1991），这可能会进一步加强养分限制并减少浮游植物生物量及其质量。因此，一方面，庇护条件似乎有利于较大的浮游动物，它们可以从容易在水柱中觅食而几乎不受悬浮沉积物干扰的情况下获利（Kirk & Gilbert,  1990）。然而，另一方面，它们可能受到浮游植物产量低及其质量的限制。因此，通过提高营养转移效率导致更高的浮游动物生物量，庇护所是否有益于更高的营养水平是值得怀疑的。相反，在遮蔽的条件下，底栖藻类和沉水植物可能是主要的生产者，而较高的营养水平可能会受益于底栖藻垫上放牧的底栖动物群、大型植物上的附生植物和大型植物本身的丰度增加（Karlsson 等，  2009 年） ，而不是增加浮游动物的产量。在后一种情况下，庇护所导致更高的食物网复杂性，提供替代途径来刺激更高的营养水平，而不是加强浮游植物-浮游动物食物链。

在这里，我们研究了避难所对初级生产者的相对优势、浮游植物和浮游动物之间的营养转移效率以及 2 个月的原地底栖动物群的影响。在荷兰新建的群岛 Marker Wadden 进行浅水操纵性野外实验。我们人为地创造了遮蔽物并操纵了沉水植物的存在，从而产生了三种处理方法：（1）无遮蔽物，（2）遮蔽物和（3）有大型植物的遮蔽物。我们假设庇护所将：（a）导致初级生产者的相对优势发生变化，预计浮游植物生物量减少，底栖藻类、大型植物和附生植物生物量增加；(b) 提高​​浮游植物和浮游动物之间的营养转移效率；(c) 增加以底栖藻类、附生植物和大型植物为食的底栖动物群的丰度。