Abstract. Biologically mediated modifications of the abiotic environment, also called ecosystem engineering, can significantly affect a broad range of ecosystems. Nevertheless, remarkably little work has focused on the costs and benefits that ecosystem engineers obtain from traits that underlie their ecosystem engineering capacity. We addressed this topic by comparing two autogenic engineers, which vary in the degree in which they affect their abiotic environment via their physical structure. That is, we compared two plant species from the intertidal coastal zone (Spartina anglica and Zostera noltii), whose shoots are exposed to similar currents and waves, but differ in the extent that they modify their environment via reduction of hydrodynamic energy. Our results indicate that there can be trade-offs related to the traits that underlies autogenic ecosystem engineering capacity. Dissipation of hydrodynamic forces from waves was roughly a factor of three higher in vegetation with stiff leaves compared to those with flexible leaves. Drag was highest and most sensitive to hydrodynamic forces in stiff vegetation that does not bend with the flow. Thus, shoot stiffness determines both the capacity to reduce hydrodynamic energy (i.e., proxy for ecosystem engineering capacity) and the drag that needs to be resisted (i.e., proxy for associated costs). Our study underlines the importance of insight in the trade-offs involved in ecosystem engineering as a first step toward understanding the adaptive nature of ecosystem engineering.

We present an overview of a large collaborative field campaign, in which we collected a long-term (months) high-resolution (4 Hz measurement frequency) hydrodynamic data set for several locations at the mudflat-salt marsh ecosystem and linked this to data on sediment transport and to a biological description of the organisms on the mudflat and the marsh. In this paper, part of this database has been used to identify general relationships that can be used for making hydrodynamic characterisations of mudflat-salt marsh ecosystems. We observed a clear linear relation between tidal amplitude and the maximum current velocity, both at the mudflat as well as within the marsh vegetation. Velocities in the vegetation were however a magnitude lower than those on the mudflat. This relationship offers promising possibilities for making hydrodynamic habitat characterisations and for validating hydrodynamic models.

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Reliable quantitative methods for sampling invertebrate communities are critical for effective freshwater biomonitoring. We tested a range of devices and protocols for sampling benthic macroinvertebrates in shallow tropical lakes; this is the first time this has been attempted in Southeast Asia. First, a pilot study to identify a suitable artificial substrate and colonisation period was conducted. Coconut brushes combined with split palm fronds attracted the greatest macroinvertebrate abundance and richness. A colonisation period of 4 wk was sufficient to capture the key macroinvertebrate families and orders. Second, the sampling efficiencies of 7 artificial substrate sampler designs and 2 hydraulic suction devices were compared in rocky and soft-sediment littoral habitats of a reservoir in Singapore. Among the 9 different sampling techniques tested, the samplers containing coconut brushes and split palm fronds again were the most effective at capturing the greatest total abundance and family richness of benthic macroinvertebrates. Variation in community structure among sampler types was largely explained by the abundance of Chironomidae and Polymitarcyidae (Ephemeroptera). Results were similar between sites dominated by 'rocky' and 'vegetated' littoral habitats. This project identified a sampling device suitable for biomonitoring Singapore's lentic environment, with protocols likely to apply to shallow tropical lentic systems elsewhere.