Max Wisshak

Ocean acidification accelerates reef bioerosion

In the recent discussion how biotic systems may react to ocean acidification caused by the rapid rise in carbon dioxide partial pressure (pCO2) in the marine realm, substantial research is devoted to calcifiers such as stony corals. The antagonistic process – biologically induced carbonate dissolution via bioerosion – has largely been neglected. Unlike skeletal growth, we expect bioerosion by chemical means to be facilitated in a high-CO2 world. This study focuses on one of the most detrimental bioeroders, the sponge Cliona orientalis, which attacks and kills live corals on Australia’s Great Barrier Reef. Experimental exposure to lowered and elevated levels of pCO2 confirms a significant enforcement of the sponges’ bioerosion capacity with increasing pCO2 under more acidic conditions. Considering the substantial contribution of sponges to carbonate bioerosion, this finding implies that tropical reef ecosystems are facing the combined effects of weakened coral calcification and accelerated bioerosion, resulting in critical pressure on the dynamic balance between biogenic carbonate build-up and degradation.

The physical niche of the bathyal Lophelia pertusa in a non-bathyal setting: environmental controls and palaeoecological implications

The habitat-forming scleractinian coral Lophelia pertusa supports an ecosystem that is widely known to occur in the bathyal marine ecologic realm along deep shelves, oceanic banks, seamounts and continental margins. Therefore, L. pertusa is generally considered a ‘deep-water’ or ‘deep-sea’ coral. In contrast, this study analyses the environmental controls of this bathyal ecosystem where it is thriving well in the non-bathyal shallow-water setting of the Swedish Kosterfjord area (NE Skagerrak). This is one of several shallow-water L. pertusa occurrences in Scandinavian waters where saline and temperature stable oceanic waters intrude as topographically-guided underflows onto the inner shelf and adjacent fjords, driven by an estuarine circulation.

Evolutionary implications of an exceptionally preserved Carboniferous microboring assemblage in the Buckhorn Asphalt lagerstätte (Oklahoma, USA)

In the Buckhorn Asphalt deposit, exceptional preservation of mollusc shells with original aragonitic mineralogy, owing to an early impregnation with migrating hydrocarbons, provides a ‘preservational window’ for studying a Late Palaeozoic microboring assemblage. The evaluation of thin-sections, bioclast surface features, and SEM analysis of epoxy resin casts reveals a total of 18 known ichnospecies and the new ichnotaxon Aurimorpha varia– reflecting the most diverse Palaeozoic microboring assemblage known to date.

Rhodolith beds (Corallinales, Rhodophyta) and their physical and biological environment at 80°31′N in Nordkappbukta (Nordaustlandet, Svalbard Archipelago, Norway)

Teichert S., Woelkerling W., Rüggeberg A., Wisshak M., Piepenburg D., Meyerhöfer M., Form A., Büdenbender J. and Freiwald A. 2012. Rhodolith beds (Corallinales, Rhodophyta) and their physical and biological environment at 80°31′N in Nordkappbukta (Nordaustlandet, Svalbard Archipelago, Norway). Phycologia 51: 371–390. DOI: 10.2216/11-76.1 Polar coralline red algae (Corallinales, Rhodophyta) that form rhodoliths have received little attention concerning their potential as ecosystem engineers and carbonate factories; although, recent findings revealed that they are much more widespread in polar waters than previously thought. The present study deals with the northernmost rhodolith communities currently known, discovered in 2006 at 80°31′N in Nordkappbukta (North Cape Bay) at Nordaustlandet, Svalbard. These perennial coralline algae must be adapted to extreme seasonality in terms of light regime (c. 4 months winter darkness), sea ice coverage, nutrient supply, turbidity of the water column, temperature and salinity. The rhodolith communities and their environment were investigated using multibeam swath bathymetry, CTD measurements, recordings of the photosynthetic active radiation (PAR) and determination of the water chemistry, seabed imaging and targeted sampling by means of the manned submersible JAGO as well as benthic collections with a dredge. The coralline flora was composed mainly of Lithothamnion glaciale, with a lesser amount of Phymatolithon tenue. Based on their distribution and development at different depth levels, a facies model was developed. Rhodoliths occurred between 30 and 51 m, while coralline algae attached to cobbles were present as deep as 78 m. Measurements of the PAR indicated their adaptation to extreme low light levels. Ambient waters were always saturated with reference to calcite and aragonite for the whole area. The rhodolith-associated macrobenthic fauna samples yielded 59 species, only one of which was typically Arctic, and the concomitant appearance of corallines and grazers kept the corallines free from epiphytes and coequally provided feeding grounds for the grazers. Overall, L. glaciale and P. tenue appeared to be well adapted to the extreme environment of the Arctic.

Bioerosion: the other ocean acidification problem

&NA; Bioerosion of calcium carbonate is the natural counterpart of biogenic calcification. Both are affected by ocean acidification (OA). We summarize definitions and concepts in bioerosion research and knowledge in the context of OA, providing case examples and meta‐analyses. Chemically mediated bioerosion relies on energy demanding, biologically controlled undersaturation or acid regulation and increases with simulated OA, as does passive dissolution. Through substrate weakening both processes can indirectly enhance mechanical bioerosion, which is not directly affected by OA. The low attention and expert knowledge on bioerosion produced some ambiguous views and approaches, and limitations to experimental studies restricted opportunities to generalize. Comparability of various bioerosion and calcification rates remains difficult. Physiological responses of bioeroders or interactions of environmental factors are insufficiently studied. We stress the importance to foster and advance high quality bioerosion research as global trends suggest the following: (i) growing environmental change (eutrophication, coral mortality, OA) is expected to elevate bioerosion in the near future; (ii) changes harmful to calcifiers may not be as severe for bioeroders (e.g. warming); and (iii) factors facilitating bioerosion often reduce calcification rates (e.g. OA). The combined result means that the natural process bioerosion has itself become a “stress factor” for reef health and resilience.

A Foraminiferal Parasite on the Sea Urchin Echinocorys: Ichnological Evidence from the Late Cretaceous (Lower Maastrichtian, Northern Germany)

In contrast to most other marine invertebrates, echinoderms favor the recognition of a syn vivo infestment of parasites and commensals by the specific response of their skeletal tissues. Attachment or embedment structures, but also repair features commonly mirror the anatomical morphology of the trace maker and may therefore be of interpretive value. Among the numerous groups of invertebrates associated with sea urchins, only a few are tightly attached to the external surface of the host, leaving visible damage on the skeleton. Here, we describe etched attachment scars, a few millimeters in size, produced by a circular to subcircular organism on the oral surface of the holasteroid echinoid Echinocorys perconica (von Hagenow, 1840) from the Lower Maastrichtian chalk of northern Germany. We compare the traces with Recent attachment scars produced by benthic foraminifers such as Hyrrokkin sarcophaga and consequently suggest a parasitic foraminifer as the most probable trace maker.

A Giant Boring in a Silurian Stromatoporoid Analysed by Computer Tomography

This study describes the largest known Palaeozoic boring trace, Osprioneides kampto igen, et isp. nov., found within a stromatoporoid Densastroma pexisum from the Upper Visby Formation (lower Wenlock, Silurian) on the island of Gotland, Sweden. Differences between the physical properties of the stromatoporoid and the dense micritic infilling of the borings allowed the application of the CT-scan technology for the 2D and 3D-visualisation of this rare trace. The additional application of a stereoscopic technique on these CT images and movies enhances its value for unravelling spatial orientations. This non-destructive method has a great potential for future macro- as well as microboring analyses. The trace maker, most likely a worm, infested the hosting colony post-mortem with up to 120 mm long borings measuring 5–17 mm in diameter. Smaller forms of Trypanites and Palaeosabella within the same stromatoporoid preferentially occur in the outer coenosteum and occasionally in abandoned borings of O. kampto. The stratigraphic position of O. kampto follows the “Great Ordovician Biodiversification Event” in time, and reflects the increase in diversity of boring species. Borings with penetration depths of 120 mm are, however, unique findings for the Palaeozoic and were not exceeded until some 260 million years later (Bajocian, Middle Jurassic) when the “Mesozoic Marine Revolution” led to convergent reinventions as a result of enhanced predation, grazing pressure, and ecospace competition.

The New Ichnogenus Flagrichnus—A Paleoenvironmental Indicator for Cold-Water Settings?

The new marine microboring ichnogenus Flagrichnus is described from Pleistocene mollusc shell beds of Rhodes (Greece) and the Costa Brava (Spain). Recent equivalents are studied in detail from the cold-temperate setting of the Swedish Kosterfjord area. Two ichnospecies are recognized: Flagrichnus profundus consists solely of a deeply penetrating gallery with a basal swelling while Flagrichnus baiulus comprises a single to multiple sack-shaped cavity at the base of a branching filamentous gallery that is penetrating deeply into the substrate. The traces are distributed from the euphotic zone down to aphotic depths suggesting (chemo)heterotrophic microendoliths and more specifically marine fungi as the trace makers. For Flagrichnus profundus, the thraustochytrid fungus Schizochytrium is recognized as its trace maker; for Flagrichnus baiulus, no definite candidate has been identified. While Flagrichnus profundus is distributed from tropical to arctic waters, Flagrichnus baiulus is only known from fossil and Recent non-tropical settings suggesting an applicability of this ichnospecies as an indicator for low paleotemperatures.

Boring a mobile domicile: an alternative to the conchicolous life habit

Conspicuous borings, belonging to the new ichnotaxon Trypanites mobilisisp. n., recorded in the bulbous spines of the echinoid Tylocidarisand in the spherical calcareous sponge Porosphaera globularis, are common in Late Cretaceous (Cenomanian) to Early Paleocene (Danian) strata of Central and NW Europe. It is suggested that the borings were produced post mortem by sipunculan worms to create a lightweight and mobile domicile, offering effective shelter and protection. This strategy, which is hitherto not known from any other animal group, represents an alternative to the conchicolous life habit. Both habits evolved almost simultaneously in sipunculans at the end of the Early Cretaceous, suggesting escalation as a response to increased predation. Moreover, it bears a number of advantages such as superior substrate availability, the avoidance of replacing the substrate during ontogeny, as well as comparatively lightweight domiciles. On the other hand, the high degree of dependence on only very few suitable specific host taxa is a major drawback of this strategy. It ultimately led to the disappearance of this mode of life in favour of the still widespread conchicolous habit at the end of the Danian when the hosts vanished together with the chalk-sea ecosystem.

A trace fossil assemblage from fluvial Old Red deposits (Wood Bay Formation; Lower to Middle Devonian) of NW‐Spitsbergen, Svalbard

From the fluvial Old Red Sandstone (ORS) of the Lower to Middle Devonian Wood Bay Formation (NW-Spitsbergen), a diverse trace fossil assemblage, including two new ichnotaxa, is described: Svalbardichnus trilobus igen. n., isp. n. is interpreted as the three-lobed resting trace of an early phyllocarid crustacean (Rhinocarididae). Cruziana polaris isp. n. yields morphological details that point towards a trilobite origin. This occurence of presumably marine trace makers in a fluvial red bed sequence raises the question of whether we are dealing with marine ingressions that are not sedimentologically expressed, with homeomorphy, or with an adaptation of marine groups to non-marine environments.