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Cryptic encrusting fauna inside invertebrate fossils from the Ordovician of Estonia

Vinn O., Ernst A., Toom U., Isakar M.

Annales Societatis Geologorum Poloniae

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2018

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Vol. 88, No. 3

285--290

EN

This is the first report of encrusted cryptic surfaces in the Ordovician of Estonia. Only bryozoans and cornulitids occurred in nautiloids and trilobites. Bryozoans were the dominant encrusters, in terms of both the number of specimens and the encrustation area. Stalked echinoderms are common on the hardgrounds in the Middle and Upper Ordovician of Baltica, but the restricted space in nautiloid living chambers and trilobites probably prevented colonization by stalked echinoderms. Cryptic surfaces in nautiloids and trilobites usually are somewhat more encrusted than the open surfaces of hardgrounds in the Ordovician of Estonia. Encrusters presumably favoured cryptic surfaces, as these were less accessible for predators and grazers. Low encrustation densities, compared to North American hard substrates, seem to be characteristic for the Ordovician Baltic Basin.

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Encrustation of inarticulate brachiopods on scaphitid ammonites and inoceramid bivalves from the Upper Cretaceous U. S. Western Interior

Landman N. H., Slattery J. S., Harries P. J.

Acta Geologica Polonica

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2016

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Vol. 66, no. 4

645--662

EN

The inarticulate brachiopod Discinisca is a rare faunal element in the Upper Cretaceous of the U.S. Western Interior. We report two occurrences of encrustation of Discinisca on a scaphitid ammonite (scaphite) and several inoceramids from the lower Maastrichtian Baculites baculus/Endocostea typica Biozones of the Pierre Shale at two localities. Six specimens of Discinisca are present on a single specimen of Hoploscaphites crassus from eastcentral Montana. They occur along the furrow at the mature apertural margin. Because the brachiopods are restricted to the margin and do not occur on the rest of the shell, it is likely that they encrusted the ammonite during its lifetime. If so, this implies that the soft body of the scaphite did not cover the outside surface of the aperture, leaving this area vulnerable to epizoan attachment. A total of 13 specimens of Discinisca are also present on four specimens of Cataceramus? barabini from east-central Wyoming. The brachiopods occur in crevices on the outside of the shells and may have encrusted the inoceramids after their death as the shells began to break down and delaminate, resulting from the decomposition of the organic matrix holding them together. Based on the faunal assemblages at both localities, the presence of Discinisca may indicate environments with either low oxygen levels and/or few predators or competitors.

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Carbon dynamics in hardwater lake: effect of charophyte biomass on carbonates deposition

Pukacz A., Pełechaty M., Frankowski M.

Polish Journal of Ecology

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2014

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Vol. 62, nr 4

695--705

EN

The photosynthetic activity of phytoplankton (in pelagial) and macrophytes (in littoral) is considered to be one of the main factors affecting the carbon cycle in lakes. This concerns in particular hardwater ecosystems, where most of the carbon is available in the form of Ca- or Mg-bicarbonates. In such ecosystems charophytes (macroscopic green algae, forming dense meadows) are regarded as the most effective carbonate producer due to the HCO3 — utilization and the formation of thick CaCO3/sub> encrustations. Calcium carbonate and biomass production of charophytes were studied in a small and shallow charophyte-dominated Lake Jasne (Western Poland). Fresh and dry weight of plants, percentage contribution of calcium carbonate and production of CaCO3 per 1 m2 were studied at three depths (1, 3 and 5 m) in three sample sites (each sampled area − 0.04 m2). Additionally, physical-chemical parameters of water samples were studied. It was found that the dry weight of charophytes and the values of calcium carbonate were similar for all sites but varied for depth of sampling. The dry weight exceeded 2000 g m-2 (average 1165 g m-2) at the most shallow sample sites. CaCO3 encrustations constituted from 39.5% at the depth of 5m, to over 82% of the charophyte dry weight at the depth of 1m. The maximum and average values of carbonates precipitated by charophytes were 1696 g m-2 and 891 g m-2, respectively, and exceeded results reported so far. The results of physical-chemical analyses revealed no statistically significant differences between all the sample sites. Nevertheless, distinct correlations were found between dry weight of charophytes, carbonates precipitated by charophytes and some physical-chemical properties of water from the sample sites. The results highlight the habitat engineering role of charophytes, evidenced in particular by great amounts of biomass influencing sedimentary processes and biogeochemical cycle within littoral zone.

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Epi- and endobionts on the late Silurian (early Pridoli) stromatoporoids from Saaremaa Island, Estonia

Vinn O., Wilson M. A.

Annales Societatis Geologorum Poloniae

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2012

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Vol. 82, No. 3

195--200

EN

A diverse sclerobiont community is described from the Kaugatuma Formation (lower Pridoli) of Saare- maa, Estonia. The stromatoporoid substrates studied here vary from low-domical to high-domical shapes. The community is numerically dominated by microconchids, which may have been characteristic of the sclerobiont fauna in the Pridoli of Baltica. Palaeoconchus aff. tenuis, Anticalyptraea calyptrata, Aulopora sp., sheet-like bryozoans, branching bryozoans, erect bryozoan holdfasts, rugosans, favositids, discoidal crinoid holdfasts, star- like crinoid holdfasts and sheet-like stromatoporoids encrust the domical stromatoporoids. Endobionts are repre- sented by embedded, symbiotic rugosans, Aulopora sp., and two rare borings Trypanites.

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Echinoids as substrates for encrustation : review and quantitative analysis

Borszcz T.

Annales Societatis Geologorum Poloniae

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2012

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Vol. 82, No. 2

139-–149

EN

The existing literature, including records of both fossil and extant echinoid encrustation, is quantitatively analysed and reviewed. This shows that echinoid encrustation (number of encrusted echinoid taphocoenoses) has increased nearly continuously and dramatically to the present day, as confirmed by linear regression values of more than 85 per cent. It also demonstrates that current levels of echinoid fouling stabilised by the Miocene, while there has been a more or less continuous record of echinoid encrustation since the Late Cretaceous. Several increases have been identified since echinoid encrustation first noted occurrence from the Late Carboniferous. This trend is explained as the probable result of corresponding increases in productivity (richness, biomass, energetics, ecospace utilisation) and resources in the marine environment, including epibionts and their hosts. This conclusion matches other indicators, including the number and thickness of shell beds, bioerosion and predation intensity or biodiversity. The trajectory might have been altered to some degree by biases (e.g. selective recording, sampling effort, outcrop area, rock volume) in the same way as palaeobiodiversity estimates. Two recognised long-term gaps in echinoid encrustation (Upper Ordovician–Lower Carboniferous and Permian–Lower Cretaceous) are explained in part as bias and as biological and taphonomic signals. These gaps are caused mostly by the rapid disarticulation of Palaeozoic-type echinoids, the methodology applied here, and a lack of interest in the encrustation of Jurassic echinoids. Conversely, three short-term gaps in the Cenozoic are interpreted exclusively as bias. If correct, the present study demonstrates quantitatively the step-wise increase of productivity through time. It also suggests potential focus on further study, including the collection of new data from the field and pre-existing collections, as best for other encrustation proxies (e.g., percent of coverage by epibionts, ratio of encrusted to nonencrusted shells, taxa richness or numerical abundance of sclerobionts) in cases of large-scale analyses.