Seagrass Patch Complexity Affects Macroinfaunal Community Structure in Intertidal Areas: An In Situ Experiment Using Seagrass Mimics

Seagrasses, as key ecosystem engineers in coastal ecosystems, contribute to enhancing diversity in comparison with nearby bare areas. It has been proved mainly for epifauna, but data on infauna are still scarce. The present study addresses how seagrass structural complexity (i.e., canopy properties) affects the diversity of infaunal organisms inhabiting those meadows. Canopy attributes were achieved using seagrass mimics, which were used to construct in situ vegetation patches with two contrasting canopy properties (i.e., shoot density and morphology) resembling the two seagrass species thriving in the inner Cadiz Bay: Zostera noltei and Cymodocea nodosa. After three months, bare nearby areas, two mimicked seagrass patches (‘Zostera’ and ‘Cymodocea’), and the surrounding natural populations of Zostera noltei were sampled in a spatially explicit way. Shifts in organism diets were also determined using 15N and 13C analyses in available food sources and main infaunal organisms, mixing models, and niche metrics (standard ellipse area). Seagrass-mimicked habitats increased the species richness (two-fold), organism abundance (three to four times), and functional diversity compared with bare nearby areas. The clam Scrobicularia plana (deposit/filter feeder) and the worm Hediste diversicolor (omnivore) were dominant in all of the samples (> 85%) and showed an opposite spatial distribution in the reconstructed patches: whilst S. plana accumulated in the outer-edge parts of the meadow, H. diversicolor abounded in the center. Changes in the isotopic signature of both species depending on the treatment suggest that this faunal distribution was associated with a shift in the diet of the organisms. Based on our results, we concluded that facilitation processes (e.g., reduction in predation and in bioturbation pressures) and changes in food availability (quality and quantity) mediated by seagrass canopies were the main driving forces structuring this community in an intertidal muddy area of low diversity.

Studies in the Wanganui Series: Pliocene Foraminifera from Wanganui Basin

<p>Foraminifera have been examined from seven Pliocene sections in South Wanganui Basin, southern North Island, New Zealand, including the Waipipian and Mangapanian Stratotypes. Lithology, faunal distribution, biostratigraphy and paleoecology are discussed for each section. The systematics and ecologic and stratigraphic ranges of 193 species are discussed. The new genus Zelamarkina is erected, with Z. excavata n.sp. as type species, and the following five species are also described as new: Bolivina hornibrooki, B. vellai, B. wanganuiensis, Rotalia fastigata and Notorotalia briggsi. Three biostratigraphic zones based on benthonic foraminifera are recognised. The Hurupiensis Zone, defined by the range of Notorotalia hurupiensis in South Wanganui Basin, is considered equivalent to the Opoitian Stage. The Molestus Zone, defined by the overlapping ranges of Cibicides molestus and Notorotalia finlayi, represents the Waipipian Stage. The Finlayi Zone equals that part of the range of N. finlayi after the extinction of Cibicides molestus, and extends through to the Recent. Temperatures dropped abruptly and markedly at the time represented by the base of the Molestus Zone, accompanied by a substantial fall in sea level, then rose at the time represented by the end of this zone to a level maintained through the period studied. No marked temperature or sea level change is recorded across the presumed Pliocene-Pleistocene boundary. The region was covered during late Miocene and early Pliocene times by shallow seas, possibly with land to the west. Rapid subsidence of the centre of the basin during the early Pliocene was followed by gradual shallowing until by the late Pliocene uniformly shallow depths again pertained. The basin was bounded to the east by the emergent Ruahine and Tararua Ranges, and probably to the south and west by shallow bars or islands formed from uplifted basement blocks. The surface microstructure of nine species of Bolivina and seven species of Notorotalia is described from scanning electron micrographs. Addition of calcite to the test of Notorotalia is progressive and is controlled largely by the positions of sutural and apertural pores.</p>

Studies in the Wanganui Series: Pliocene Foraminifera from Wanganui Basin

<p>Foraminifera have been examined from seven Pliocene sections in South Wanganui Basin, southern North Island, New Zealand, including the Waipipian and Mangapanian Stratotypes. Lithology, faunal distribution, biostratigraphy and paleoecology are discussed for each section. The systematics and ecologic and stratigraphic ranges of 193 species are discussed. The new genus Zelamarkina is erected, with Z. excavata n.sp. as type species, and the following five species are also described as new: Bolivina hornibrooki, B. vellai, B. wanganuiensis, Rotalia fastigata and Notorotalia briggsi. Three biostratigraphic zones based on benthonic foraminifera are recognised. The Hurupiensis Zone, defined by the range of Notorotalia hurupiensis in South Wanganui Basin, is considered equivalent to the Opoitian Stage. The Molestus Zone, defined by the overlapping ranges of Cibicides molestus and Notorotalia finlayi, represents the Waipipian Stage. The Finlayi Zone equals that part of the range of N. finlayi after the extinction of Cibicides molestus, and extends through to the Recent. Temperatures dropped abruptly and markedly at the time represented by the base of the Molestus Zone, accompanied by a substantial fall in sea level, then rose at the time represented by the end of this zone to a level maintained through the period studied. No marked temperature or sea level change is recorded across the presumed Pliocene-Pleistocene boundary. The region was covered during late Miocene and early Pliocene times by shallow seas, possibly with land to the west. Rapid subsidence of the centre of the basin during the early Pliocene was followed by gradual shallowing until by the late Pliocene uniformly shallow depths again pertained. The basin was bounded to the east by the emergent Ruahine and Tararua Ranges, and probably to the south and west by shallow bars or islands formed from uplifted basement blocks. The surface microstructure of nine species of Bolivina and seven species of Notorotalia is described from scanning electron micrographs. Addition of calcite to the test of Notorotalia is progressive and is controlled largely by the positions of sutural and apertural pores.</p>

The recovery of early vertebrates and reef ecosystems following the late Silurian carbon isotope excursion: the Burgen outlier, Gotland, Sweden

&lt;p&gt;The Ludfordian Carbon Isotope Excursion (LCIE) reached the highest known &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C values in the Phanerozoic. It was a global environmental perturbation manifested in a rapid regression attributed to glacial eustasy. Previous studies suggested that it has also heavily affected the diversity of conodonts, early vertebrates and reef ecosystems, but the timing of the crisis and recovery remained complicated owing to the lateral variability of &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C values in epeiric platforms and rapid facies shifts, which drove faunal distribution. One of the best records of this interval is available in the Swedish island of Gotland, which preserves tectonically undisturbed strata deposited in a Silurian tropical carbonate platform. We revisited the world-renowned collection of the late Lennart Jeppsson, hosted at the Swedish Museum of Natural History, Stockholm, which holds the key to reconstruct the dynamics of faunal immigration and diversification following the LCIE. Here we focus on the Burgen erosional outlier, which remained a mystery, as it had been correlated with the excursion strata, but preserved a high diversity of conodonts and reefal ecosystems. We re-examined key outcrops and characterized macro- and microfacies, as well as chemostratigraphy and unpublished fauna in the collection. Strata in the Burgen outlier&amp;#160;represent back-shoal facies of the Burgsvik Oolite Member and correspond to the Ozarkodina snajdri Conodont Biozone. The shallow-marine position compared to the more continental setting of coeval strata in southern Gotland, is reflected in the higher &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;carb&lt;/sub&gt; values, reaching +9.2&amp;#8240;. The back-shoal succession in this outcrop includes reefs, which contain a large proportion of microbial carbonates and have therefore been previously compared with low-diversity buildups developed in a stressed ecosystem. However, the framework of these reefs is built by a diverse coral-stromatoporoid-bryozoan fauna, indicating that a high microbial contribution might be a characteristic of the local carbonate factory rather than a reflection of restricted conditions.&amp;#160;In the case of conodonts, impoverishment following the LCIE might be a product of facies preferences, as the diverse environments in the outlier yielded at least 20 of the 21 species known from the Burgsvik Formation in Gotland. Fish diversity also returned to normal levels following the LCIE with an estimated minimum of 9 species. Thelodont scales appear to dominate samples from the Burgen outlier, which is in line with previous reports. Our observations highlight how palaeoenvironmental reconstructions inform fossil niche and diversity analyses, but also how fossil museum collections continuously contribute new data on past biodiversity.&lt;/p&gt;

Unraveling the effects of environmental drivers and spatial structure on benthic species distribution patterns in Eurasian-Arctic seas (Barents, Kara and Laptev Seas)

In times of accelerating climate change, species are challenged to respond to rapidly shifting environmental settings. Yet, faunal distribution and composition are still scarcely known for remote and little explored seas, where observations are limited in number and mostly refer to local scales. Here, we present the first comprehensive study on Eurasian-Arctic macrobenthos that aims to unravel the relative influence of distinct spatial scales and environmental factors in determining their large-scale distribution and composition patterns. To consider the spatial structure of benthic distribution patterns in response to environmental forcing, we applied Moran’s eigenvector mapping (MEM) on a large dataset of 341 samples from the Barents, Kara and Laptev Seas taken between 1991 and 2014, with a total of 403 macrobenthic taxa (species or genera) that were present in ≥ 10 samples. MEM analysis revealed three spatial scales describing patterns within or beyond single seas (broad: ≥ 400 km, meso: 100–400 km, and small: ≤ 100 km). Each scale is associated with a characteristic benthic fauna and environmental drivers (broad: apparent oxygen utilization and phosphate, meso: distance-to-shoreline and temperature, small: organic carbon flux and distance-to-shoreline). Our results suggest that different environmental factors determine the variation of Eurasian-Arctic benthic community composition within the spatial scales considered and highlight the importance of considering the diverse spatial structure of species communities in marine ecosystems. This multiple-scale approach facilitates an enhanced understanding of the impact of climate-driven environmental changes that is necessary for developing appropriate management strategies for the conservation and sustainable utilization of Arctic marine systems.

On the diversity of amphipods inhabiting Sargassum as well as clear areas in Kuwait coastal waters, with an assessment of the effect of turbidity and notes on their abundance, composition, and distribution: a preliminary study

The distribution and abundance patterns of amphipods associated with Sargassum species were studied on a spatial scale along Kuwait’s coastal waters. Macroalgae, in particular Sargassum spp., are known to host a high biodiversity of marine fauna, particularly amphipods, when compared to non-Sargassum (“clear”) areas. Amphipods are an important component in the food web, being consumed by different stages of fish. Sargassum was sampled from four different stations in Kuwait’s waters to determine the amphipod species composition and density. Physicochemical parameters were measured at the time of sampling at each station, focusing on turbidity, as this can promote variation in the faunal distribution between areas, and it was the only non-biological factor showing a distinctive pattern between stations in this study. The objectives of this study thus were to describe the amphipod biodiversity in Sargassum communities and to measure the difference in diversity between Sargassum and clear areas, while concurrently taking into account the effect of turbidity. The most abundant amphipods represented were Pontocrates sp. (cf. arenarius (Spence Bate, 1858)), Ericthonius sp. (cf. forbesii Hughes & Lowry, 2006), Maxillipius rectitelson Ledoyer, 1973, and Podocerus mamlahensis Myers & Nithyanandan, 2016. Among the measured physicochemical parameters, only turbidity had a significant effect on the biodiversity of amphipods (, ) with a negative relationship based on the general linear model test. The effect of Sargassum and non-Sargassum areas on amphipod diversity was statistically not significant (, ). Also, there was no interaction between turbidity and Sargassum/clear areas (, ). However, the diversity was observed to be higher in Sargassum areas of all stations as compared to their clear counterparts, except in Khairan during January 2016, where the situation was the opposite. The abundance was highest in low turbidity, particularly at Salmyia station, compared to the high turbidity conditions at the stations at Failaka and Green Island. The species composition differed as well, the number of species found being the highest in the Sargassum area of Salmyia Station and the lowest at Failaka Island (highest turbidity). Only Salmyia Station (low turbidity) contained 27 species in its Sargassum area, of which only few were present at other stations in both areas. Turbidity affected the diversity of amphipods, and diversity was higher in Sargassum areas at all stations except Khairan in January 2016, but that difference was not significant.