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Justin B Ries - One of the best experts on this subject based on the ideXlab platform.
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increased production of calcite and slower growth for the major sediment producing Alga halimeda as the mg ca ratio of seawater is lowered to a calcite sea level
Journal of Sedimentary Research, 2010Co-Authors: Steven M Stanley, Justin B Ries, Lawrence A HardieAbstract:Abstract Laboratory experiments were conducted to subject the Calcareous Alga Halimeda, a prolific producer of aragonite in the modern ocean, to a variety of ambient Mg/Ca ratios. These experiments were based on three predictions: (1) that Halimeda would calcify at a lower rate when the ambient Mg/Ca ratio was reduced from its high level in modern seawater (5.2); (2) that this Alga would grow more slowly under these conditions because its calcification yields as a byproduct CO2, which is available for photosynthesis; and (3) that the calcite content of Halimeda’s skeleton would increase as a percentage of total CaCO3. As predicted, reduction of the Mg/Ca ratio of ambient artificial seawater from its modern level to estimated early Oligocene and early Eocene levels (2.5 and 1.5, respectively) resulted in progressively lower rates of calcification, production of organic matter, and linear growth for Halimeda incrassata colonies. The ambient Mg/Ca ratio exerted a stronger influence over the rate of calcification than [Ca2+], which in the geologic past has risen in seawater whenever the ambient Mg/Ca ratio has declined. Thus, although elevation of [Ca2+] at such times would have promoted the calcification and growth of Halimeda, the concomitant decline of the Mg/Ca ratio would have had a stronger negative effect. In addition, the percentage of skeletal material consisting of calcite rose from 8% in modern-day seawater to 16% in artificial early Oligocene seawater and 46% in artificial early Eocene seawater. Magnesium was incorporated into this calcite as a function of the ambient Mg/Ca ratio with a fractionation pattern differing only slightly from that of nonskeletal calcite. Halimeda exerts less biological control over its biomineralization than the related genera Penicillus and Udotea, which in previous experiments produced only 22–25% of skeletal CaCO3 as calcite in seawater having a very low Mg/Ca ratio (1.0). Nonetheless, it is likely that many taxa of green Algae that produce little or no calcite today would have produced a substantial proportion of skeletal low-Mg CaCO3 as calcite in ancient seas, such as those of the Cretaceous, whose Mg/Ca ratios were close to unity.
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aragonite production in calcite seas effect of seawater mg ca ratio on the calcification and growth of the Calcareous Alga penicillus capitatus
Paleobiology, 2005Co-Authors: Justin B RiesAbstract:Abstract Previous studies have shown that secular variation in the Mg/Ca ratio of seawater throughout the Phanerozoic would have subjected the aragonite-producing codiacean Algae to at least three transitions between the low-Mg calcite (molar Mg/Ca 2) nucleation fields in the oceans, since their origin in the Ordovician. These studies have asserted that major sediment production by codiacean Algae in Recent tropical seas is permitted by the Mg/Ca ratio of modern seawater (molar Mg/Ca ∼5.2) remaining within the aragonitic/high-Mg calcite nucleation field (molar Mg/Ca >2). Here I present the results of experiments conducted to determine the effects of ambient Mg/Ca on the mineralogy, growth rate, primary productivity, calcification rate, and biomechanics of the codiacean Alga Penicillus capitatus. P. capitatus specimens were grown in three artificial seawater treatments that mimic ancient seawater of differing Mg/Ca ratios, corresponding to the low-Mg calcit...
Bruno Granier - One of the best experts on this subject based on the ideXlab platform.
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a new and unique bodyplan in fossil bryopsidales with description of jaffrezocodium bipennatus n gen n sp an albian cenomanian Calcareous green Alga
Cretaceous Research, 2018Co-Authors: Bruno GranierAbstract:Abstract This short contribution deals with a fossil Calcareous Alga found in (?) Albian and Cenomanian strata of N Spain and S France. This taxon is characterized by its uncommon and previously misinterpreted bodyplan. Its rhombic sections were first ascribed to a puzzling form of Dasycladales, but they prove to belong to Bryopsidales.
Felix Schlagintweit - One of the best experts on this subject based on the ideXlab platform.
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new observations on permocalculus gosaviensis schlagintweit 1991 Calcareous Alga from the upper cretaceous of the northern Calcareous alps gosau group austria
Studia Universitatis Babes-bolyai Geologia, 2010Co-Authors: Felix SchlagintweitAbstract:New thin-sections from the Upper Cretaceous Gosau Group of Brandenberg, Tyrol, Austria, yielded well-preserved specimens of the Calcareous Alga Permocalculus gosaviensis SCHLAGINTWEIT. Microfacies are foraminiferal-Algal wackestones; stratigraphy is Upper Turonian (? Lower Coniacian). It is shown that the original description was based on oblique sections leading to the incorrect assumption of a piryform segment morphology. Instead, P. gosaviensis is a representative of Permocalculus of the group with constrictions/swellings along the segments (waxing-and-waning type). Permocalculus nikolapantici RADOICIC from the Upper Turonian of Serbia is considered a junior synonym of Permocalculus gosaviensis SCHLAGINTWEIT.
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neomeris mokragorensis sp nov Calcareous Alga dasycladales from the cretaceous of serbia montenegro and the northern Calcareous alps gosau group austria
Geoloski Anali Balkanskog Poluostrva, 2007Co-Authors: Rajka Radoicic, Felix SchlagintweitAbstract:The new species of the genus Neomeris - Neomeris mokragorensis sp. nov. described in this paper from western Serbia originates: from the Albian of Mokra Gora (the succession transgrading on the serpenti- nite) and from the Turonian of the Skrape`-Kosjeri} area (the succession transgrading on the Carboniferous). The presence of this species has been noted in the Turonian of the Kukes and in the Santonian of the Meto- hija Cretaceous Unit (Mirdita Zone). In the surrounding of Podgorica (Dinaric Carbonate Platform, Montenegro), the same species previously was presented as Neomeris cf cretacea STEINMANN. Well preserved Neomeris speci- mens from the Turonian to the Santonian strata of the Northern Calcareous Alps (Gosau Group, Austria) pre- viously described as Neomeris circularis BADVE & NAYAK, is assigned to Neomeris mokragorensis sp. nov. Neomeris mokragorensis is characterized by a thin loosed skeleton formed only around ampullae, by which, besides the form of the ampullae, this species is clearly distinct from Neomeris cretacea (Steinmann).
Branko Sokac - One of the best experts on this subject based on the ideXlab platform.
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montenegrella gracilis n sp a new Calcareous Alga dasycladales from the upper barremian of mt biokovo dinarides mts croatia
Geologia Croatica, 2015Co-Authors: Branko Sokac, Tonci GrgasovicAbstract:Montegrella? gracilis n.sp. (Dasycladales) is characterized by thick Calcareous envelope and narrow central cavity. Bipartite branches are arranged alternately in consecutive whorls. The primaries are visibly differentiated into a thin, tendril-like stalk in the proximal part and a club-shaped or ellipsoidal inflated swelling in the distal part. The secondaries are poorly visible, of unclear shape and number, with a supposedly common starting point. On the type-locality, the Alga occurs within a rich, typically Upper Barremian, Algal assemblage. The validity of the genus Montenegrella , being disputed by BARATTOLO (1983), is commented upon by showing the generic attribution of the same or different species either to Suppiluliumaella or to Montenegrella by different authors.
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clypeina lagustensis n sp a new Calcareous Alga from the lower tithonian of the lastovo island croatia
Geologia Croatica, 2014Co-Authors: Branko Sokac, Tonci Grgasovic, Antun HusinecAbstract:Clypeina lagustensis n.sp. has been found in the Lower Tithonian deposits of the Lastovo Island (Dalmatia, Croatia). It is visually similar, obviously related and in some sections appearing almost identical, to Clypeina jurassica FAVRE, from which it differs by visible swellings and thinning of the central cavity, more pronounced distance between neighbouring whorls of fertile branches, and shape and structure of the interverticillate thallus parts, characterized by having well developed, hairy, sterile branches. These, after emerging from the exit pore, divide into several bundles which form a common turf with a Calcareous envelope in the proximal part. Normal 0 21 false false false HR X-NONE X-NONE
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linoporella vesiculifera n sp a new Calcareous Alga dasycladales from the upper barremian of mt biokovo karst dinarides croatia
Geologia Croatica, 2010Co-Authors: Branko SokacAbstract:According to all the main characteristics, the new species belongs to the genus Linoporella. At the species-specific level, Linoporella vesiculifera n.sp. is characterized by visibly widened distal ends of the secondary branches, which gives a vesiculiferous appearance to the outer surface of the thallus. The distal widenings are spherically or conically shaped and open outwards in a funnel-like form. A short review of the taxonomic validation of some Linoporella species is also given. The new species is derived from the Barremian deposits of Mt. Biokovo (central Dalmatia, Croatia).
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Asterocalculus heraki n. gen., n. sp., a new Calcareous Alga (gymnocodiaceae) from the Upper Triassic hauptdolomite of Žumberak, north Croatia
Facies, 1998Co-Authors: Branko Sokac, Tonći GrgasovićAbstract:A sample of Upper Triassic, early diagenetic, peritidal dolomite (Hauptdolomite) from western Žumberak (north Croatia) contains a new species of Calcareous Algae (family Gymnocodiaceae). The new Algal species is accompanied by rich foraminiferal assemblage consisting of numerous Triasina hantkeni, Auloconus permodiscoides , and Aulotortus sinuousus and less numerous Aulotortus friedli and A. tenuis . The new Algal species is represented by numerous variously oriented sections which enable the accurate description and interpretation of its morphologic features of both outer shape and inner structure. In the present paper the new Algal species is described as Asterocalculus heraki n. gen., n. sp., characterized by a cylindrical thallus with loosely spaced levels of tubular protrusions, supposedly functioning as another type of reproductive structures, in addition to ‘conceptacles’, or having some unknown physiological function.
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dissocladella bystrickyi n sp a new Calcareous Alga dasycladaceae from upper triassic dolomites of mt medvednica northern croatia
Geologia Croatica, 1995Co-Authors: Branko Sokac, Tonci GrgasovicAbstract:Dissocladella bystrickyi n.sp. occurs in early diagenetic Upper Triassic dolomites, that were deposited in tidal flat and tidal channel environments in the carbonate platform interior. The new Alga, assigned to the genus Dissocladella, is characterized by verticillate and distally flattened primary ramifications which give rectangular pores and each bear 5-7 club-shaped secondaries. Its stratigraphic position is probably within the Norian-Rhaetian.
James A. Powell - One of the best experts on this subject based on the ideXlab platform.
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characterizing manatee habitat use and seagrass grazing in florida and puerto rico implications for conservation and management
Pacific Conservation Biology, 1999Co-Authors: Lynn W Lefebvre, James P Reid, W. Judson Kenworthy, James A. PowellAbstract:The Indian River Lagoon on the Atlantic coast of Florida, USA, and the east coast of Puerto Rico provide contrasting environments in which the endangered West Indian Manatee Trichechus manatus experiences different thermal regimes and seagrass communities. We compare Manatee feeding behaviour in these two regions, examine the ecological effects of Manatee grazing on a seagrass community in the Indian River Lagoon, describe the utility of aerial surveys, radio tracking, and seagrass mapping to study Manatee feeding patterns, and develop hypotheses on sirenian feeding strategies in temperate and tropical seagrass communities. In both the Indian River Lagoon and Puerto Rico, Manatees were typically observed grazing in water depths = 2.0 m and more frequently on the most abundant seagrasses present in the community: Halodule wrightii in the Indian River Lagoon and Thalassia testudinum in eastern Puerto Rico. Where both H. wrightii and Syringodium filiforme were consumed in the Indian River Lagoon, Manatees tended to remove more S. filiforme than H. wrightii rhizome + root biomass. Even though 80 to 95% of the short-shoot biomass and 50 to 67% of the rhizome + root biomass were removed, grazed patches of H. wrightii and S. filiforme recovered significantly between February and August. H. wrightii may be both more resistant and resilient than S. filiforme to the impacts of Manatee grazing. Despite the significantly greater abundance of T. testudinum in Puerto Rico, Manatees exhibited selective feeding by returning to specific sites with abundant H. wrightii. They also appeared to feed selectively on T. testudinum shoots associated with clumps of the Calcareous Alga Halimeda opuntia. We hypothesize that Florida Manatees are less specialized seagrass grazers than Manatees in tropical regions like Puerto Rico. Continued research on Manatee grazing ecology in temperate to tropical seagrass communities will enable better protection and management of these vital and unique marine resources.