Benthic Substrate Research Articles

Spatial Heterogeneity of Air–Sea Energy Fluxes over a Coral Reef—Heron Reef, Australia

AbstractThe thermal environment of a coral reef is moderated by complex interactions of air–sea heat and moisture fluxes, local to synoptic-scale weather and reef hydrodynamics. Measurements of air–sea energy fluxes over coral reefs are essential to understanding the reef–atmosphere processes that underpin coral reef environmental conditions such as water temperature, cloud, precipitation, and local winds (such as during coral bleaching events). Such measurements over coral reefs have been rare, however, and the spatial heterogeneity of surface–atmosphere energy exchanges due to the different geomorphic and biological zones on coral reefs has not been captured. Accordingly, the heterogeneity of coral reefs with regard to substrate, benthic communities, and hydrodynamic processes has not been considered in the characterization of the surface radiation budget and energy balance of coral reefs. Here, the first concurrent in situ eddy covariance measurements of the surface energy balance and radiation transfers over different geomorphic zones of a coral reef are presented. Results showed differences in radiation transfers and sensible and latent heat fluxes over the reef, with higher Bowen ratios over the shallow reef flat zone. The energy flux divergence between sites increased with wind speed and during unstable, southeasterly trade winds with the net flux of heat being positive and negative over different geomorphic zones. The surface drag coefficient at measurement height ranged from 1 × 10−3 to 2.5 × 10−3, with no significant difference between sites. Results confirm that spatial variation in radiation and air–reef–water surface heat and moisture fluxes occurs across a lagoonal platform reef in response to local meteorological conditions, hydrodynamics, and benthic–substrate cover.

A combined sensor for simultaneous high resolution 2‐D imaging of oxygen and trace metals fluxes

A new sandwich sensor, consisting of an O2 planar optode overlain by a thin (90 µm) DGT layer is presented. This sensor can simultaneously resolve 2‐D O2 dynamics and trace metal fluxes in benthic substrates at a high spatial resolution. The DGT layer accumulates metals on a small particle size (0.2 µm) chelating resin and records the locally induced trace metal flux during the deployment, whereas the planar optode resolves the O2 dynamic in near real time at the same location in the sediment. Despite its ultrathin composition, the DGT layer has high carrying capacity for trace metals with no saturation problems during application to typical coastal‐ or contaminated sediments. Combined with laser ablation, accumulated metal fluxes could be resolved at a resolution of ~200 µm, whereas the O2 images had a resolution of ~100 µm. A 2‐D diffusion‐reaction model showed that the enhanced smearing and reduced response time of the O2 signal associated with the additional DGT layer were marginal. To test sensor performance at realistic conditions, it was applied to an artificial burrow system consisting of permeable dialysis tubing flushed with oxygenated seawater. The measurements demonstrated localized mobilization of Ni, Cu, and Pb close to the burrow wall, where O2 was elevated. The latter was also confirmed for Cu and Pb in natural sediments irrigated by the polychaete Hediste diversicolor. The sandwich sensor has great potential for investigating interrelations between O2 dynamics and metal mobilization in complex benthic systems such as burrows, rhizospheres, permeable sands, and microbial mats.

Light detection and ranging (LiDAR) and multispectral studies of disturbed Lake Superior coastal environments

Due to its high spatial resolution and excellent water penetration, coastal light detection and ranging (LiDAR) coupled with multispectral imaging (MSS) has great promise for resolving shoreline features in the Great Lakes. Previous investigations in Lake Superior documented a metal‐rich “halo” around the Keweenaw Peninsula, related to past copper mining practices. Grand Traverse Bay on the Keweenaw Peninsula provides an excellent Great Lakes example of global mine discharges into coastal environments. For more than a century, waste rock migrating from shoreline tailings piles has moved along extensive stretches of coast, damming stream outlets, intercepting wetlands and recreational beaches, suppressing benthic invertebrate communities, and threatening critical fish breeding grounds. In the bay, the magnitude of the discarded wastes literally “reset the shoreline” and provided an intriguing field experiment in coastal erosion and spreading environmental effects. Employing a combination of historic aerial photography and LiDAR, we estimate the time course and mass of tailings eroded into the bay and the amount of copper that contributed to the metal‐rich halo. We also quantify underwater tailings spread across benthic substrates by using MSS imagery on spectral reflectance differences between tailings and natural sediment types, plus a depth‐correction algorithm (Lyzenga Method). We show that the coastal detail from LiDAR and MSS opens up numerous applications for ecological, ecosystem, and geological investigations.

The Distribution ofCordulegaster(Odonata: Cordulegastridae) Nymphs in Seeps and Springs of Nelson Swamp (Madison County, NY)

Abstract Given the presence of foraging and reproducing adult Cordulegaster (spiketail) dragonflies in Nelson Swamp (Madison County, NY), we examined nymph distribution and abundance in the seeps and springs found within the swamp. From 9 September–4 November 2010, we surveyed 8 sites along Chittenango Creek in order to determine: (1) the species present and their distribution/occurrence among sites, (2) factors influencing species presence and abundances, and (3) patterns in size and age distribution among and within sites. For sites, we delineated habitat zones (inlet, middle, outlet), determined the benthic substrate, and measured shoreline perimeters. For nymphs, we measured head width, body length, and wing pad length and identified some to species. The majority of spiketails we identified were Cordulegaster diastatops (Delta-spotted Spiketail); Cordulegaster maculata (Twin-spotted Spiketail) was also present. Most nymphs occurred in inlets with muck and cobble bottoms and in water depths less than 1...

Seasonal and microhabitat influences on diatom assemblages and their representation in sediment traps and surface sediments from adjacent High Arctic lakes: Cape Bounty, Melville Island, Nunavut

The spatial (i.e. microhabitat) and temporal (i.e. seasonal) characteristics of diatom assemblages in adjacent High Arctic lakes were studied intensively June–August 2004. These baseline data are used to improve understanding of modern diatom community dynamics, as well to inform paleoenvironmental reconstructions. Diatoms were collected approximately weekly through the melt season from each principal benthic substrate (moss/macrophyte, rock scrapes, littoral sediment), plankton, and sediment traps, and were compared to the uppermost 0.5 cm of a surface core obtained from the deepest part of the lake where sediment cores are routinely collected. Water samples were collected concurrently with diatom samples to investigate species–environment relationships. The lakes share approximately half of their common taxa, the most abundant overall in both lakes being small Cyclotella species. Results of detrended correspondence analysis (DCA) indicate that the largest gradient in species turnover existed between benthic and planktonic communities in both lakes, and that sediment trap and the surface core top samples most closely resemble the planktonic assemblage, with an additional contribution from the lotic environment. Our results indicate clear micro-spatial controls on species assemblages and a degree of disconnection between the benthos and deep lake sediments that manifests as an under-representation of benthic taxa in deep lake surface sediments. These findings are particularly relevant in the context of interpreting the paleoenvironmental record and assessing ecosystem sensitivity to continued climate change.

Marine habitat mapping in support of Marine Protected Area management in a subarctic fjord: Gilbert Bay, Labrador, Canada

This paper presents an approach that allows production of benthic substrate and habitat maps in fjord environments. This approach is used to support the management of the Gilbert Bay Marine Protected Area (MPA) in southeastern Labrador, Atlantic Canada. Multibeam sonar-derived bathymetry, seabed slope, and acoustic reflectance (backscatter) were combined using supervised classification methods and GIS with ground-truthed benthic sampling in order to derive maps of the substrates and main benthic habitats. Six acoustically distinct substrate types were identified in the fjord, and three additional substrate types without a unique acoustic signature were recognized. Ordination by multidimensional scaling and analysis of similarity generalized these to four acoustically distinct habitat types. Greatest within-habitat (alpha) diversity was found in the coralline-algae encrusted gravel habitat. Greatest between-habitat (beta) diversity was found in the management Zones 1 and 2, which have the highest level of protection. The study confirmed that the zoning plan for the MPA, which was designed to protect spawning and juvenile fish habitat for a local genetically distinct population of Atlantic cod, afforded highest levels of protection to areas with highest habitat diversity.

Estimation of spawning habitats of market squid (Doryteuthis opalescens) from field surveys of eggs off Central and Southern California

AbstractLike many other loliginid squid, Doryteuthis (Loligo) opalescens deposits egg cases on the ocean floor. Depending upon temperature, egg cases may persist for 5–12 weeks before the paralarvae hatch. Because of this relatively long duration and squid’s pelagic life history, egg cases provide a practical life stage to survey. During 2001–2002, squid egg beds in Monterey Bay, Carmel Bay, and around the California Channel Islands were surveyed using a remotely operated vehicle with the goal of delineating the habitat of egg beds that are spawned during active commercial fishing. Egg cases were highly aggregated and densities reached 1338 capsules m−2. Squid eggs were significantly shallower in Central California. Egg cases occurred between 20 and 93 m around the Channel Islands, and in Central California they were between 13 and 61 m. The temperatures in both regions were similar (10–12 °C), with some eggs in Southern California found up to 14.4 °C. Ninety‐five percent of eggs were found on sand, suggesting that temperature and substrate are stronger behavioral cues than depth to stimulate spawning. Suitable spawning habitat was defined by three criteria: sandy benthic substrate, temperatures between 10 and 14.4 °C, and depths between 20 and 70 m when the first two criteria hold. Additionally, within this defined area, oxygen concentration is quantified. The greatest commercial landings of market squid occur in both Central and Southern California during a time of year when water temperatures of 10–12 °C are prevalent in the 20–70 m depth range.

Effects of hurricanes on the stability of reef-associated landscapes

The effects of Hurricane Emily (July 2005, Category 4) on nine different benthic substrates in the reef-associated landscape along the west coast of Cozumel (Mexico) were evaluated by comparing the cover of nine types of substrate on ground-truthed sites before (ten months) and after (two months) the hurricane. Four substrates showed significant differences (Wilcoxon signed-rank test, P < 0.05). Coverage of sand and sand over rock increased, while that of seagrass and hard corals decreased. The effects of the hurricane on soft corals diminished below 10 m depth. Sites between 0.5 and 5.5 m were less affected towards the southwest of the island, where the reefs are more developed. Algal cover was similar to pre-hurricane values after two months, which suggests fast algal recolonization. Cozumel reefs are considered to be healthy; however, a possible increase in the abundance of macroalgae as a result of hurricanes coupled with poorly regulated tourism activities could eventually favor a phase shift in the system.

Spatial and Temporal Comparisons of Benthic Composition at Necker Island, Northwestern Hawaiian Islands

Necker Island, a remote island located in the Northwestern Hawaiian Islands, provides a unique opportunity to investigate species-level algal and benthic invertebrate assemblages and assess temporal variation of coral reef ecosystems exposed to minimal anthropogenic impacts. This study provides a robust baseline of common benthic species at Necker Island and their relative abundances before any known ecological response to changing oceanographic conditions. Rapid ecological assessment (REA) methods using photoquadrat imagery from long-term monitoring sites coupled with towed-diver surveys conducted between 2002 and 2006 were analyzed to determine percentage cover of benthic organisms around the island, and macroalgal species lists were compiled from voucher specimens. Benthic substrates were typically dominated by turf algae at all sites for all years, and macroalgal and coral covers were found to be low. A total of 25 macroalgal and 11 anthozoan species was identified. Of these, 13 macroalgal species and one coral species represent new records for Necker Island. Analyses of community similarity found spatial differences among sites in 2006, as well as temporal differences between 2005 and 2006, an outcome primarily driven by significant increases in percentage cover of macroalgae and coral at one site. However, benthic communities observed during extensive towed-diver surveys around Necker Island did not identify significant differences among geographical sectors or years, suggesting that benthic communities are relatively homogeneous. Necker Island contains macroalgal and coral populations similar to those of neighboring reef systems within the Northwestern Hawaiian Islands, and this study provides a baseline of benthic assemblages for ongoing temporal monitoring.

The use of background matching vs. masquerade for camouflage in cuttlefish Sepia officinalis

Cuttlefish, Sepia officinalis, commonly use their visually-guided, rapid adaptive camouflage for multiple tactics to avoid detection or recognition by predators. Two common tactics are background matching and resembling an object (masquerade) in the immediate area. This laboratory study investigated whether cuttlefish preferentially camouflage themselves to resemble a three-dimensional (3D) object in the immediate visual field (via the mechanism of masquerade/deceptive resemblance) rather than the 2D benthic substrate surrounding them (via the mechanisms of background matching or disruptive coloration). Cuttlefish were presented with a combination of benthic substrates (natural rocks or artificial checkerboard and grey printouts) and 3D objects (natural rocks or cylinders with artificial checkerboards and grey printouts glued to the outside) with visual features known to elicit each of three camouflage body pattern types (Uniform, Mottle and Disruptive). Animals were tested for a preference to show a body pattern appropriate for the 3D object or the benthic substrate. Cuttlefish responded by masquerading as the 3D object, rather than resembling the benthic substrate, only when presented with a high-contrast object on a substrate of lower contrast. Contrast is, therefore, one important cue in the cuttlefish’s preference to resemble 3D objects rather than the benthic substrate.

Artificial Neural Network (ANN) Based Inversion of Benthic Substrate Bottom Type and Bathymetry in Optically Shallow Waters - Initial Model Results

Ocean-colour remote sensing in optically shallow waters is influenced by contribution from the water column depth as well as by the substrate type. Therefore, it is required to include the contribution from the water column and substrate bottom type for bathymetry estimation. In this report we demonstrate the use of Artificial Neural Network (ANN) based approach to spectrally distinguish various benthic bottom types and estimate depth of substrate bottom simultaneously in optically shallow waters. We have used in-water radiative transfer simulation modeling to generate simulated top-of-the-water column reflectance the four major benthic bottom types viz. sea grass, coral sand, green algae and red algae using Hydrolight simulation model. The simulated remote sensing reflectance, for the four benthic bottom types having benthic bottom depth up to 30 m were generated for moderately clear waters. A multi-layer perceptron (MLP) type neural network was trained using the simulated data. ANN based approach was used for classification of the benthic bottom type and simultaneous inversion of bathymetry. Simulated data was inverted to yield benthic bottom type classification with an accuracy of ~98% for the four benthic substrate types and the substrate depth were estimated with an error of 0% for sea grass, 1% for coral sand and 1–3% for green and red algae up to 25 m, whereas for substrate bottom deeper than 25 m depth the classification errors increased by 2–5% for three substrate bottom types except sea grass bottom type. The initial results are promising which needs validation using the in-situ measured remote sensing reflectance spectra for implementing further on satellite data.

Dimorphism in methane seep-dwelling ecotypes of the largest known bacteria

We present evidence for a dimorphic life cycle in the vacuolate sulfide-oxidizing bacteria that appears to involve the attachment of a spherical Thiomargarita-like cell to the exteriors of invertebrate integuments and other benthic substrates at methane seeps. The attached cell elongates to produce a stalk-like form before budding off spherical daughter cells resembling free-living Thiomargarita that are abundant in surrounding sulfidic seep sediments. The relationship between the attached parent cell and free-living daughter cell is reminiscent of the dimorphic life modes of the prosthecate Alphaproteobacteria, but on a grand scale, with individual elongate cells reaching nearly a millimeter in length. Abundant growth of attached Thiomargarita-like bacteria on the integuments of gastropods and other seep fauna provides not only a novel ecological niche for these giant bacteria, but also for animals that may benefit from epibiont colonization.

Land use influences stream nitrate uptake in the Lake Taupo catchment

We quantified nitrate (NO3 −) uptake during summer for 11 streams draining into oligotrophic Lake Taupo. Nitrate uptake lengths (S w ) ranged from 258 to 12035 m, uptake velocities (V f ) ranged from 0.2 to 6.8 m/day and removal efficiencies (P r ) ranged from 1% to 59%. Nitrate uptake velocities and areal uptake rates were, respectively, 9- and 26-fold higher for streams in pasture and pine forest land use than in native vegetation. However, average NO3 − export from these streams was also 8-fold higher. Our results suggested that NO3 − uptake velocity (V f ) was highest in streams with higher dissolved phosphorus (P) concentrations and flow velocities, and smaller benthic substrate size, which were characteristic of catchments dominated by pasture and pine forest land use. Uptake (as removal efficiency, P r ) accounted for an average 16% of the stream NO3 − export to Lake Taupo. However, since most uptake is assimilatory, removal from the water column is likely to only represent temporary sequestration of NO3 − and a conversion of inorganic to organic and/or particulate N.

Remote Sensing of Shallow Coastal Benthic Substrates: In situ Spectra and Mapping of Eelgrass (Zostera marina) in the Gulf Islands National Park Reserve of Canada

Eelgrass (Zostera marina) is a keystone component of inter- and sub-tidal ecosystems. However, anthropogenic pressures have caused its populations to decline worldwide. Delineation and continuous monitoring of eelgrass distribution is an integral part of understanding these pressures and providing effective coastal ecosystem management. A proposed tool for such spatial monitoring is remote imagery, which can cost- and time-effectively cover large and inaccessible areas frequently. However, to effectively apply this technology, an understanding is required of the spectral behavior of eelgrass and its associated substrates. In this study, in situ hyperspectral measurements were used to define key spectral variables that provide the greatest spectral separation between Z. marina and associated submerged substrates. For eelgrass classification of an in situ above water reflectance dataset, the selected variables were: slope 500–530 nm, first derivatives (R’) at 566 nm, 580 nm, and 602 nm, yielding 98% overall accuracy. When the in situ reflectance dataset was water-corrected, the selected variables were: 566:600 and 566:710, yielding 97% overall accuracy. The depth constraint for eelgrass identification with the field spectrometer was 5.0 to 6.0 m on average, with a range of 3.0 to 15.0 m depending on the characteristics of the water column. A case study involving benthic classification of hyperspectral airborne imagery showed the major advantage of the variable selection was meeting the sample size requirements of the more statistically complex Maximum Likelihood classifier. Results of this classifier yielded eelgrass classification accuracy of over 85%. The depth limit of eelgrass spectral detection for the AISA sensor was 5.5 m.

A new genus and species of surgeon fish (Perciformes, Acanthuridae) from the Oligocene of Kanton Glarus, Switzerland

The new genus and species of surgeon fish, Glarithurus friedmani (Acanthuridae), from the Lower Oligocene (Rupelian) of Kanton Glarus, Switzerland, differs from all other acanthurid fishes, fossil and extant, by having a single anal-fin basal pterygiophore situated in the first interhaemal space, versus two or more such pterygiophores in all other taxa. The new taxon is based upon a 29-mm SL acronurus stage specimen that probably had already settled onto a benthic substrate from its pelagic larval stage and begun its transformation into a juvenile. It has a scalpel-like dermal spine on the caudal peduncle and a crest on the hyomandibular, which are derived characters that establish it as a member of the clade of higher acanthurins. Within that clade, it is unique because of the great depth of its basipterygium at the subpelvic keel.

Comparative predation rates on larval snappers (Lutjanidae) in oceanic, reef, and nearshore waters

The life cycle of most reef fishes involves pelagic larvae entering the nearshore environment to settle to benthic substrates. Settlement is considered to be highly risky as larvae encounter high rates of predation mortality associated with shallow nearshore habitats. This potential bottleneck may be particularly significant for many tropical snapper (Lutjanidae) species which bypass the reef to settle to very nearshore seagrass areas. To test the hypothesis that predation-related mortality increases as naïve late-stage fish larvae leave the offshore oceanic environment and enter the nearshore to settle, relative nocturnal predation rates on tethered late-stage snapper larvae were measured in oceanic, coral reef, and nearshore surface waters of the lower Florida Keys, USA. Both relative predation rate and probability of predation in oceanic areas seaward of the reef was significantly greater than over reef or nearshore seagrass/hardbottom habitats. This surprising result may be due to differences in the density or spatial distribution of potential predators between deep offshore (near flotsam at the surface) and shallow nearshore environments (demersal). These findings suggest that successful late-stage snapper larvae should avoid surface waters in deep oceanic areas and move upward in the water column as they pass over the reef and other shallow nearshore environments prior to settlement.

Development Strategy Of Yellow Tail Fusilier Fish (Caesio cuning) Resources Management on Coral Ecosystem in The Seribu Islands

Population of Yellow tail fusilier fish (Caesio cuning) in Seribu Islands at this time has decreased. The main caus e of decreas ing in abundance of the fish is due to degradation of coral reef ecosystem as a habitat of the fish. The purpose s of the study is to examine the association of Yellow tail fusilier fish resources with habitat characteristics. The study was conducted in the Seribu Islands waters o n May 2009, at the four islands, each consisting of two observation locations. Percentage benthic substrate cover, and the number of coral lifeform using the Square Transect method, while to see the abundance of the fish resources using Underwater Visual Cencus. Bent hic substrate cover was dominated by abiotic cover ( 36.42% ) , hard coral cover was in fair condition ( 32.27%) , dominated by foliose coral, massive coral, a cropora branching and encrusting coral. The abundance of Yellow tail fusilier fish was 67 individu/250 m 2 . North Pramuka, West Panggang, and South Panggang was only observed some small fishes. Closing area can be implemented for management purposes with the combination of introducing brooder. In vise versa East Pramuka and East Kayu Angin have been observed only adult fishes. Closing area can be implemented for management purposes with the combination of introducing juveniles. In West Kayu Angin closing area can be implemented to give the opportunity juvenile for growing and adult for breading. South Belanda have all range of size fishes as well as good condition of habitat. It is therefore, this can be developed as marine protected area with eco-freienly marine tourism activities. Keywords: coral reef ecosystem, fish resources, yellow tail fusilier fish, habitat linkages, Seribu islands .

The effect of landscape composition and configuration on the spatial distribution of temperate demersal fish

In contrast to the terrestrial environment, where the use of landscape analyses has been clearly demonstrated, the influence of landscape composition and configuration on the abundance and spatial distribution of marine organisms remains poorly understood. Development of this area of marine research has been limited by the lack of accurate benthic habitat maps, particularly for marine environments deeper than can be penetrated by optical remote sensing ( < 10 m). However, the recent availability of detailed (1:25 000) and accurate habitat maps derived from hydroacoustic surveys of deeper marine waters has redressed this situation. The aim of this research was to establish the strength and significance of derived landscape composition and configuration indices on the demersal fish assemblage structure and spatial distribution. A combination of depth and 6 landscape measures were found to explain 34.8% of the variation in the fish assemblage. Depth contributed the highest percentage of the variance explained, accounting for 23.7%. Distance to reef was the most important landscape index explaining 7.1% of the variability, followed by total length of edge environment (the interface between different benthic substrates) explaining 1.5%. Species responsible for driving the structure of the fish assemblage were also examined and found to respond not only to the proximity of reef but also to the configuration of the reef. For example, Parika scaber and Pseudolabrus psittaculus characterised more heterogeneous landscapes offering clusters of small interconnected patches of reef with a lot of edge environment, whilst juvenile Trachyurus novaezelandiae and Platycephalus caeruleopunctatus preferred more homogeneous landscapes offering little reef or edge environment. This research demonstrated that a broad scale landscape analysis, employing indices of landscape composition and configuration, is important for understanding demersal fish assemblage structure and spatial distribution.

Plankton of the central Great Barrier Reef: abundance, production and trophodynamic roles

The abundance, composition and metabolic activity of plankton were assessed in the Tribulation zone of the central Great Barrier Reef (16°–17°S). Wet phytoplankton biomass ranged in shallow reef waters from 30 to 70 mg m−3, and from 60 to 270 mg m−3in the deep lagoon and in the estuarine areas which are dominated by pico- and nano-algae. Wet bacterioplankton biomass varied from 70 to 290 mg m−3. Wet meroplankton biomass was less than 10 mg m−3. Wet daytime mesozooplankton biomass ranged from 100 to 300 mg m−3in the deep lagoon. In the estuarine area, it reached 400 to 1300 mg m−3and in the shallow inner lagoon of the Low Isles ring reef it varied from 10 to 30 mg m−3. Zooplankton density increased at night and was 3 to 5 fold greater in the deep lagoon, for about 2 orders of magnitude greater over the reef shallows and up to 3 orders of magnitude greater in mangrove habitats, due to the emergence of demersal components from the benthos. The biomass of zooplankton hidden in the benthic substrates during the day reached 10 to 40 g m−2. Pelagic primary production in the deep lagoon varied between 0.2 and 0.5 g C m−2 d−1. A calculation of the energy balance suggests that the basic energy source for heterotrophic plankton production in the deep lagoon is the organic matter exported from surrounding reef benthic communities and from mangroves. The trophic status of coral reef pelagic ecosystem might range from mesotrophic to eutrophic.

Does ambient substrate composition influence consumer diversity effects on algal removal?

Benthic substrates constitute an important habitat template for aquatic communities and may affect the contributions of benthic organisms to ecological processes. To test the effects of ambient substrate composition on the process of algae accrual and removal, we conducted an experiment to examine how substrate type influenced consumer richness effects. We hypothesized that algal removal from focal substrates (ceramic tiles) would be influenced by the surrounding ambient substrate through its effect on nutrient cycling and subsequent algal growth. We manipulated consumer richness in mesocosms at one or three species while holding consumer biomass constant. Aquatic consumers were an amphipod, a snail, and a water boatman, and ambient substrates were either sand or gravel. After 21 days, ambient substrate influenced epilithic algal accrual on tiles, affected physio-chemical parameters within mesocosms, and modified consumer behavior. Chlorophyll a was approximately 2× greater on control tiles surrounded by sand, and FPOM and turbidity were greater on sand than gravel when consumers were present. Substrate modified consumer behavior such that consumers congregated around focal substrates in sand, but dispersed around them in gravel. Consumers also had substrate-specific influences on epilithic chlorophyll, causing a decrease in sand and an increase in gravel. Algal assemblages on focal tiles were dominated by diatoms, and their composition responded to consumer richness and identity, but not substrate. Our data suggest that direct effects (e.g., consumptive removal of epilithon from focal tiles) were more pronounced in sand, whereas indirect effects (e.g., bioturbation and enhanced mixing) promoted algal accrual in gravel. These results show that algae production on exposed surfaces may change as underlying substrate composition changes, and that substrate type can alter consumer diversity effects on algal removal.