Interactions between Sponges and the Water Column: Nutrient Utilisation and Feeding by New Zealand Subtidal Sponges

<p>Sponges are an important component of New Zealand subtidal communities and play many key functional roles in marine ecosystems, including competition for space, facilitating primary production, nutrient cycling, bioerosion, and interactions with the water column. Sponges are involved in the bidirectional movement of detritus, nutrients, micro-organisms and planktonic particles both to and from the benthos to the pelagic ecosystem, thereby affecting pelagic processes. As suspension-feeders, sponges are capable of filtering large volumes of water, and they depend on food that is suspended in the water column, meaning that their interaction with the water column is likely to be very important. The main goal of my research was to investigate the interactions between sponges and the water column and how this varies in relation to sponge characteristics, nutrient fluxes, seasonality and food supply. I studied the diet composition of 10 sponge species that are abundant and widely distributed along the south coast of Wellington, New Zealand. I found that the diet of the sponge species analysed comprised three types of picoplanktonic organisms: heterotrophic bacteria, Prochlorococcus, and Synechococcus. These micro-organisms (picoplankton) that sponges feed on are vital for benthic food webs because they are involved in the transformation and cycling process of dissolved inorganic nutrients before they become available to other marine organisms. The results from this thesis demonstrated that different sponge species have different retention efficiencies for different types of picoplankton and I propose that this suggests intra-phyletic food particle niche partitioning among sponges. While these findings support the partitioning of food resources between different co-existing sponge species, they also suggest that partitioning may not be essential for co-existence, as some species had similar retention efficiencies implying an overlap in resource use. By measuring rates of carbon assimilation in the form of planktonic food particles, combined with data on a number of characteristics of the sponge species analysed, I found that sponge assemblages play a key role in the transfer of energy from the water column to the benthos. The results from this thesis indicate that there is a wide range of food concentrations in the rocky reefs where the study species are living, over which retention rate, nutrient utilisation and carbon consumption varied temporally. This emphasises the importance of understanding temporal variation in productivity, and suggests that such variations are likely to have important implications for suspension-feeders. By integrating the feeding results with estimations of oxygen consumption rates, and the amount of carbon obtained from the different micro-organisms found in the water column, preliminary carbon budgets were created. These budgets were used to quantify the capacity of carbon obtained via heterotrophic suspension-feeding to support sponge metabolism, as well as infer the potential for this carbon to support other processes such as sponge growth and reproduction. Overall, this project was the first to consider the functional roles of sponges in New Zealand marine ecosystems and provided useful information on their ecological and biological importance. The large amounts of carbon that sponges transfer from the water column to the benthos, in conjunction with the other findings of my thesis, increase our understanding of the ecology of temperate sponges.</p>

Interactions between Sponges and the Water Column: Nutrient Utilisation and Feeding by New Zealand Subtidal Sponges

<p>Sponges are an important component of New Zealand subtidal communities and play many key functional roles in marine ecosystems, including competition for space, facilitating primary production, nutrient cycling, bioerosion, and interactions with the water column. Sponges are involved in the bidirectional movement of detritus, nutrients, micro-organisms and planktonic particles both to and from the benthos to the pelagic ecosystem, thereby affecting pelagic processes. As suspension-feeders, sponges are capable of filtering large volumes of water, and they depend on food that is suspended in the water column, meaning that their interaction with the water column is likely to be very important. The main goal of my research was to investigate the interactions between sponges and the water column and how this varies in relation to sponge characteristics, nutrient fluxes, seasonality and food supply. I studied the diet composition of 10 sponge species that are abundant and widely distributed along the south coast of Wellington, New Zealand. I found that the diet of the sponge species analysed comprised three types of picoplanktonic organisms: heterotrophic bacteria, Prochlorococcus, and Synechococcus. These micro-organisms (picoplankton) that sponges feed on are vital for benthic food webs because they are involved in the transformation and cycling process of dissolved inorganic nutrients before they become available to other marine organisms. The results from this thesis demonstrated that different sponge species have different retention efficiencies for different types of picoplankton and I propose that this suggests intra-phyletic food particle niche partitioning among sponges. While these findings support the partitioning of food resources between different co-existing sponge species, they also suggest that partitioning may not be essential for co-existence, as some species had similar retention efficiencies implying an overlap in resource use. By measuring rates of carbon assimilation in the form of planktonic food particles, combined with data on a number of characteristics of the sponge species analysed, I found that sponge assemblages play a key role in the transfer of energy from the water column to the benthos. The results from this thesis indicate that there is a wide range of food concentrations in the rocky reefs where the study species are living, over which retention rate, nutrient utilisation and carbon consumption varied temporally. This emphasises the importance of understanding temporal variation in productivity, and suggests that such variations are likely to have important implications for suspension-feeders. By integrating the feeding results with estimations of oxygen consumption rates, and the amount of carbon obtained from the different micro-organisms found in the water column, preliminary carbon budgets were created. These budgets were used to quantify the capacity of carbon obtained via heterotrophic suspension-feeding to support sponge metabolism, as well as infer the potential for this carbon to support other processes such as sponge growth and reproduction. Overall, this project was the first to consider the functional roles of sponges in New Zealand marine ecosystems and provided useful information on their ecological and biological importance. The large amounts of carbon that sponges transfer from the water column to the benthos, in conjunction with the other findings of my thesis, increase our understanding of the ecology of temperate sponges.</p>

Devonian agglutinated polychaete tubes: all in all it's just another grain in the wall

Biomineralized and organic metazoan tubular skeletons are by far the most common in the fossil record. However, several groups of organisms are also able to agglutinate particles to construct more rigid structures. Here we present a novel type of agglutinated tube from the austral and endemic palaeobiota of the Malvinokaffric realm (Devonian, Brazil). This fossil is characterized by an agglutinated tube made of silt-sized particles forming an unusual flanged morphology that is not known from the fossil record. Besides being able to select specific particles, these organisms probably lived partially buried and were detritus/suspension feeders. Comparisons across different modern groups show that these fossils are strongly similar to tubes made by polychaetes, specifically from the family Maldanidae. If this interpretation is correct, then an early divergence of the Sedentaria clade may have occurred before the Devonian.

Ross Sea Benthic Ecosystems: Macro- and Mega-faunal Community Patterns From a Multi-environment Survey

The Ross Sea, Antarctica, is amongst the least human-impacted marine environments, and the site of the world’s largest Marine Protected Area. We present research on two components of the Ross Sea benthic fauna: mega-epifauna, and macro-infauna, sampled using video and multicore, respectively, on the continental shelf and in previously unsampled habitats on the northern continental slope and abyssal plain. We describe physical habitat characteristics and community composition, in terms of faunal diversity, abundance, and functional traits, and compare similarities within and between habitats. We also examine relationships between faunal distributions and ice cover and productivity, using summaries of satellite-derived data over the decade prior to our sampling. Clear differences in seafloor characteristics and communities were noted between environments. Seafloor substrates were more diverse on the Slope and Abyss, while taxa were generally more diverse on the Shelf. Mega-epifauna were predominantly suspension feeders across the Shelf and Slope, with deposit feeder-grazers found in higher or equal abundances in the Abyss. In contrast, suspension feeders were the least common macro-infaunal feeding type on the Shelf and Slope. Concordance between the mega-epifauna and macro-infauna data suggests that non-destructive video sampling of mega-epifauna can be used to indicate likely composition of macro-infauna, at larger spatial scales, at least. Primary productivity, seabed organic flux, and sea ice concentrations, and their variability over time, were important structuring factors for both community types. This illustrates the importance of better understanding bentho-pelagic coupling and incorporating this in biogeographic and process-distribution models, to enable meaningful predictions of how these ecosystems may be impacted by projected environmental changes. This study has enhanced our understanding of the distributions and functions of seabed habitats and fauna inside and outside the Ross Sea MPA boundaries, expanding the baseline dataset against which the success of the MPA, as well as variability and change in benthic communities can be evaluated longer term.

The Importance of Food Pulses in Benthic-Pelagic Coupling Processes of Passive Suspension Feeders

Benthic-pelagic coupling processes and the quantity of carbon transferred from the water column to the benthic suspension feeders needs multiple intensive sampling approaches where several environmental variables and benthos performance are quantified. Here, activity, dietary composition, and capture rates of three Mediterranean gorgonians (Paramuricea clavata, Eunicella singularis, and Leptogorgia sarmentosa) were assessed in an intensive cycle considering different variables such as the seston concentration and quality (e.g., carbon, nitrogen, and zooplankton), the colony branch patterns, and the energetic input of the single species (i.e., mixotrophic and heterotrophic). The three species showed clear differences in their impact on the seston concentration. Paramuricea clavata, the most densely distributed, showed a greater impact on the near bottom water column seston. The lowest impact of E. singularis on the seston could be explained by its mixotrophy and colony branching pattern. Leptogorgia sarmentosa had a similar impact as E. singularis, having a much more complex branching pattern and more than an order of magnitude smaller number of colonies per meter square than the other two octocorals. The amount of carbon ingested in the peaks of the capture rates in the three species may cover a non-neglectable proportion of the potential carbon fluxes.

Active carpets drive non-equilibrium diffusion and enhanced molecular fluxes

Biological activity is often highly concentrated on surfaces, across the scales from molecular motors and ciliary arrays to sessile and motile organisms. These ‘active carpets’ locally inject energy into their surrounding fluid. Whereas Fick’s laws of diffusion are established near equilibrium, it is unclear how to solve non-equilibrium transport driven by such boundary-actuated fluctuations. Here, we derive the enhanced diffusivity of molecules or passive particles as a function of distance from an active carpet. Following Schnitzer’s telegraph model, we then cast these results into generalised Fick’s laws. Two archetypal problems are solved using these laws: First, considering sedimentation towards an active carpet, we find a self-cleaning effect where surface-driven fluctuations can repel particles. Second, considering diffusion from a source to an active sink, say nutrient capture by suspension feeders, we find a large molecular flux compared to thermal diffusion. Hence, our results could elucidate certain non-equilibrium properties of active coating materials and life at interfaces.

Biogeography of benthic foraminifera in contourite drift systems

&lt;div&gt; &lt;p&gt;&lt;span&gt;Benthic foraminifera colonize a wide range of marine environments, including contourite drift systems (CDS). CDS are characterized by sustained bottom currents and cover large areas on the seafloor, e.g., in the North Atlantic. Due to their high sedimentation rates, they represent fundamental archives for paleoclimatology and paleoceanography. Some studies already highlight the influence of high current velocities on assemblages of epibenthic foraminifera and suggest their applicability as a reliable proxy for bottom current reconstructions (Sch&amp;#246;nfeld, 2002; Jorissen et al., 2007 and references therein). Certain epibenthic foraminiferal species live as highly adapted opportunistic suspension feeders using elevated substrates as a unique ecological niche. Through their elevated microhabitat, they optimize the uptake of suspended food particles gaining an advantage over other epibenthic organisms. However, their application as a bottom current proxy has so far been limited to the Iberian Margin and has been barely tested outside the Gulf of Cadiz (e.g., Diz et al., 2004).&lt;/span&gt;&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;&lt;span&gt;The present study aims to document biogeographic distribution patterns of benthic foraminifera in extended CDS from different latitudes. Two data sets from the high-latitude North Atlantic (50-62&amp;#176;N) are presented here. The surface samples of the first data set originate from the Bj&amp;#246;rn and Gardar drifts between the Reykjanes Ridge and the Rockall Plateau south of Iceland. Deposition is primarily controlled by the Iceland Scotland Overflow Water. The second data set is located further west within the Eirik Drift on the southern slope of the Greenland margin. The main controlling water mass is the Deep Western Boundary Current.&lt;/span&gt;&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;&lt;span&gt;Initial results show that epibenthic species dominate over infaunal taxa. The data set is mainly determined by the tubular agglutinated species &lt;em&gt;Rhabdammina abyssorum&lt;/em&gt;, &lt;em&gt;Saccorhiza ramosa&lt;/em&gt;, and &lt;em&gt;Rhizammina algaeformis&lt;/em&gt;, as well as hyaline forms such as &lt;em&gt;Hoeglundina elegans&lt;/em&gt;, &lt;em&gt;Cibicidoides wuellerstorfi&lt;/em&gt;, and &lt;em&gt;Cibicides refulgens&lt;/em&gt;. &lt;/span&gt;&lt;span&gt;Thus, several different suspension-feeding taxa dominate the data set. Three assemblages of benthic foraminifera are distinguished: agglutinated suspension feeders dominating in more clayey environments, hyaline suspension feeders dominating in sandier environments with increased current velocities, and infaunal detritus feeders dominating below 2000 m water depth.&lt;/span&gt;&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;&lt;span&gt;The presented data sets are currently complemented by samples from the Campos drift on the Brazilian margin (10&amp;#176;-22&amp;#176;S). Together, the low, mid and high latitude data sets will improve our understanding of biogeographic distribution patterns of benthic foraminifera in CDS. The expected results will be fundamental to ensure the applicability of foraminifera-based proxy methods for bottom current reconstruction.&lt;/span&gt;&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;&lt;strong&gt;&lt;span&gt;References&lt;/span&gt;&lt;/strong&gt;&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;&lt;span&gt;Diz, P., Guillermo, F., Costas, S., Souto, C., Alejo, I., 2004. Distribution of benthic foraminifera in coarse sediments, Ria de Vigo, NW Iberian Margin. &lt;/span&gt;J. Foraminifer. Res. 34, 258&amp;#8211;275. https://doi.org/10.2113/34.4.258&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;Jorissen, F.J., Fontanier, C., Thomas, E., 2007. &lt;span&gt;Paleoceanographical proxies based on deep-sea benthic foraminiferal assemblage characteristics, in: Hillaire-Marcel, C., de Vernal, A. (Eds.), Proxies in Late Cenozoic Paleoceanography: Pt. 2: Biological Tracers and Biomarkers. pp. 263&amp;#8211;325. https://doi.org/10.1016/S1572-5480(07)01012-3&lt;/span&gt;&lt;/p&gt; &lt;/div&gt;&lt;div&gt;&lt;span&gt;Sch&amp;#246;nfeld, J., 2002. Recent benthic foraminiferal assemblages in deep high-energy environments from the Gulf of Cadiz (Spain). &lt;/span&gt;&lt;/div&gt;&lt;p&gt;Mar. Micropaleontol. 44, 141&amp;#8211;162. https://doi.org/10.1016/S0377-8398(01)00039-1&lt;/p&gt;

Capture of conspecific planktonic larvae by the suspension-feeding gastropod Crepipatella peruviana: association between adult and larval size

ABSTRACT Free-living, planktonic larvae can be vulnerable to capture and ingestion by adult suspension-feeders. This is particularly the case for larvae that settle gregariously in benthic environments where suspension-feeders occur at high densities. Larvae of gregarious suspension-feeding species are at particularly high risk, as adults of their own species often serve as cues for metamorphosis. We conducted laboratory experiments to assess the extent to which adults of the suspension-feeding caenogastropod Crepipatella peruviana would capture and ingest their own larvae. Experiments were conducted with adults of different sizes, with larvae of different ages and sizes, and in the presence or absence of phytoplankton. Adults captured larvae in all experiments. The presence of microalgae in the water did not influence the extent of larval capture. On average, 39% of larvae were captured during the 3-h feeding periods, regardless of adult size. However, up to 34% of the larvae that were captured on the gill were later discarded as pseudofaeces; the other 64% were ingested. The extent of capture by adults was not related to adult size, or to larval size and, thus, to larval age. Our results suggest that the filtration of congeneric larvae by adult C. peruviana is a result of accidental capture rather than a deliberate feeding preference. Such ingestion could, however, still be an important source of larval mortality, especially when the advanced larvae of this species are searching for a suitable substrate for metamorphosis.

The effect of external flow on the feeding currents of sessile microorganisms

Microscopic sessile suspension feeders live attached to surfaces and, by consuming bacteria-sized prey and by being consumed, they form an important part of aquatic ecosystems. Their environmental impact is mediated by their feeding rate, which depends on a self-generated feeding current. The feeding rate has been hypothesized to be limited by recirculating eddies that cause the organisms to feed from water that is depleted of food particles. However, those results considered organisms in still water, while ambient flow is often present in their natural habitats. We show, using a point-force model, that even very slow ambient flow, with speed several orders of magnitude less than that of the self-generated feeding current, is sufficient to disrupt the eddies around perpendicular suspension feeders, providing a constant supply of food-rich water. However, the feeding rate decreases in external flow at a range of non-perpendicular orientations due to the formation of recirculation structures not seen in still water. We quantify the feeding flow and observe such recirculation experimentally for the suspension feeder Vorticella convallaria in external flows typical of streams and rivers.

Global gradients in intertidal species richness and functional groups

Whether global latitudinal diversity gradients exist in rocky intertidal α-diversity and across functional groups remains unknown. Using literature data from 433 intertidal sites, we investigated α-diversity patterns across 155° of latitude, and whether local-scale or global-scale structuring processes control α-diversity. We, furthermore, investigated how the relative composition of functional groups (algae, grazers, predators and suspension-feeders) changes with latitude. α-diversity differed among hemispheres with a mid-latitudinal peak in the north, and a non-significant unimodal pattern in the south, but there was no support for a latitudinal diversity gradient. Although global-scale drivers had no discernible effect, the local-scale drivers significantly affected α-diversity, and our results reveal that latitudinal diversity gradients are outweighed by local-processes. In three functional groups: predators, grazers and suspension-feeders diversity declined with latitude, coinciding with an inverse gradient in algae. Overall, we propose more studies are needed on the magnitude and influence of physical and biotic drivers across multiple scales.