Topic
Chondrus
About: Chondrus is a research topic. Over the lifetime, 129 publications have been published within this topic receiving 4443 citations.
Papers published on a yearly basis
Papers
TL;DR: Results of manipulations during both primary and secondary succession indicate that Littorina littorea, the only large, abundant herbivore in the low zone, has no direct effect on perennating or established Chondrus, or on its extensive, encrusting holdfast.
Abstract: This paper analyzes the factors controlling the development and persistence of patterns of distribution, abundance, and diversity of space users in the low rocky intertidal zone of New England. The spatial structure of this community changes along a wave exposure gradient. Mussels (Mytilus edulis) dominate at headlands exposed to wave shock, the alga Chondrus crispus (Irish moss) dominates at sites protected from wave shock, and both are abundant at areas intermediate in exposure to waves. Using a combination of experiments (exclosures, enclosures, removals) and observations, we evaluated the effects of several factors on this system, including (1) predation, (2) herbivory, (3) plant—plant competition, (4) plant—animal competition, and (5) physical disturbance from high—energy waves. The interaction having the greatest effect on the structure of this low zone association was predation. At protected sites, the starfish Asterias forbesi, Asterias vulgaris, and the snail Thais lapillus prey heavily on Mytilus, which is the functionally dominant competitor in the low (and mid) zone(s). When secondary succession is initiated by removal of all erect animals and plants, community development in the absence of these predators (predator exclusion) results in competitive elimination of both the barnacle Balanus balanoides and Chondrus by Mytilus. A similar result occurs if predators are excluded from unaltered stands of Chondrus. Controls in these experiments (i.e., with predators present) usually either developed to, or remained as stands of Chondrus. At intermediate sites, patches of Mytilus occassionally escaped from predation, suggesting predation intensity is patchy in space and time. Persistence of Chondrus is thus a by—product of the activities of predators at protected sites. At exposed sites, predators do not control the mussels. As a consequence, Mytilus outcompetes Chondrus and Balanus for space and achieves structural dominance. Periwinkle abundance decreases, and abundance and seasonality of ephemeral algae increase with increasing wave shock. Results of manipulations during both primary and secondary succession indicate that Littorina littorea, the only large, abundant herbivore in the low zone, has no direct effect on perennating (regrowing vegetatively) or established Chondrus, or on its extensive, encrusting holdfast. However, this periwinkle exerts an important indirect effect by consuming seasonally abundant ephemeral algae, which slow the rate of succession by suppressing growth of Chondrus. Once Chondrus is established, L. littorea damps variations in its abundance by cropping epiphytic ephemeral algae. The role of other herbivores seems negligible. Experiments show that limpets and sea urchins potentially could control Chondrus (and its holdfast), but they are normally too scarce to have a detectable effect on the algae. Chondrus thus monopolizes space at protected areas because (1) its competitors (mussels and epiphytic ephemeral algae) are removed by their consumers (predators and herbivores), (2) it has escaped control by herbivores, and (3) it can outcompete other perennial algae by virtue of its ability to perennate, and thus maintain its occupancy of space. The organization of this portion of the New England rocky intertidal region is thus similar in important ways to that of the mid zone (Menge 1975, 1976). Predation intensity, at least partly a function of wave shock, is great at relatively protected sites and determines the observed structural pattern (domination of space by algae). Since consumers are ineffective in controlling prey at exposed sites, mussels outcompete other space users and monopolize space on the shore. Thus, predators apparently determine the "trajectory" followed during succession. The persistence of algae is strongly dependent on the removal of mussels by predators. Herbivores, though ineffective in controlling the structurally dominant perennial algae, control the abundance of ephemeral algae and hence both determine the rate at which a Chondrus bed develops and stablize established beds of Irish moss by reducing variability in its abundance. Thus, herbivores evidently control the rate of community development (succession) and enhance the persistence of this alga. Disturbance from wave shock seems to operate in a fashion similar to both types of consumers by removing mussels and ephemeral algae. However, this sort of removal tends to be more catastrophic, frequently clearing large areas of space and initiating secondary succession, especially at exposed sites. The role of disturbance is thus largely that of inducing, rather than suppressing, variability in this system.
650 citations
Pierre-and-Marie-Curie University1, University of Évry Val d'Essonne2, French Alternative Energies and Atomic Energy Commission3, Centre national de la recherche scientifique4, Alfred Wegener Institute for Polar and Marine Research5, University of Ostrava6, Queen's University Belfast7, University of Rennes8, Pompeu Fabra University9, University of Oslo10, Scottish Association for Marine Science11, American University in Cairo12, University of Freiburg13, University of Marburg14
TL;DR: An evolutionary scenario involving an ancestral red alga that was driven by early ecological forces to lose genes, introns, and intergenetic DNA is proposed; this loss was followed by an expansion of genome size as a consequence of activity of transposable elements.
Abstract: Red seaweeds are key components of coastal ecosystems and are economically important as food and as a source of gelling agents, but their genes and genomes have received little attention. Here we report the sequencing of the 105-Mbp genome of the florideophyte Chondrus crispus (Irish moss) and the annotation of the 9,606 genes. The genome features an unusual structure characterized by gene-dense regions surrounded by repeat-rich regions dominated by transposable elements. Despite its fairly large size, this genome shows features typical of compact genomes, e.g., on average only 0.3 introns per gene, short introns, low median distance between genes, small gene families, and no indication of large-scale genome duplication. The genome also gives insights into the metabolism of marine red algae and adaptations to the marine environment, including genes related to halogen metabolism, oxylipins, and multicellularity (microRNA processing and transcription factors). Particularly interesting are features related to carbohydrate metabolism, which include a minimalistic gene set for starch biosynthesis, the presence of cellulose synthases acquired before the primary endosymbiosis showing the polyphyly of cellulose synthesis in Archaeplastida, and cellulases absent in terrestrial plants as well as the occurrence of a mannosylglycerate synthase potentially originating from a marine bacterium. To explain the observations on genome structure and gene content, we propose an evolutionary scenario involving an ancestral red alga that was driven by early ecological forces to lose genes, introns, and intergenetic DNA; this loss was followed by an expansion of genome size as a consequence of activity of transposable elements.
370 citations
TL;DR: The photosynthesis of green and brown algae with thin thalli decreased in green light, but species with thick thalli from these two groups had action spectra which were almost flat, and matched the optical blackness of the thalli but did not reflect the pigment differences between the species.
Abstract: Net photosynthesis at 10μmol photons m-2 s-1 in each of 24 wavelengths was measured in absolute units by an O2-electrode and corrected for dark respiration to construct action spectra for gross photosynthesis in nine species of algae, which included plants with thin and thick thalli from each of four major pigment groups. The photosynthesis of green and brown algae with thin thalli decreased in green light, but species with thick thalli from these two groups had action spectra which were almost flat, and matched the optical blackness of the thalli but did not reflect the pigment differences between the species. Among the red algae, on the other hand, there was little difference between the action spectra for thin and thick algae. Only wavelengths absorbed by the phycobilin pigments were effective in photosynthesis, even in species (e.g. Chondrus, Phyllophora) which absorbed all visible wavelengths strongly. Maximal quantum yields of 0.10 to 0.12 O2 molecules per absorbed photon were recorded for thin green and brown algae, but thicker algae in these two groups had lower values. Red algae exhibited maximal values close to 0.10 O2 molecules per absorbed photon, irrespective of thallus thickness or phycocyanin content, but the quantum yields of phycoerythrin-rich species in the 600 to 650 nm waveband were lower than those of phycocyanin-rich species.
154 citations
TL;DR: In this paper, UVR is used to determine the upper depth distribution limit of macroalgae on the shore and the degree of UV-induced inhibition of photosynthesis is lower in eulittoral species and higher in sublittoral ones.
Abstract: The reproductive cells of macroalgae are regarded as the life history stages most susceptible to various environmental stresses, including UV radiation (UVR). UVR is proposed to determine the upper depth distribution limit of macroalgae on the shore. These hypotheses were tested by UV-exposure experiments, using spores and young thalli of the eulittoral Rhodophyceae Mastocarpus stellatus and Chondrus crispus and various sublittoral brown macroalgae (Phaeophyceae) with different depth distribution from Helgoland (German Bight) and Spitsbergen (Arctic). In spores, the degree of UV-induced inhibition of photosynthesis is lower in eulittoral species and higher in sublittoral species. After UV stress, recovery of photosynthetic capacity is faster in eulittoral compared to sublittoral species. DNA damage is lowest while repair of DNA damage is highest in eulittoral compared to sublittoral species. When the negative impact of UVR prevails, spore germination is inhibited. This is observed in deep water kelp species whereas the same UVR doses do not inhibit germination of shallow water kelp species. A potential acclimation mechanism to increase UV tolerance of brown algal spores is the species-specific ability to increase the content of UV-absorbing phlorotannins in response to UV-exposure. Growth rates of young Mastocarpus and Chondrus gametophytes exposed to experimental doses of UVR are not affected while growth rates of all young kelp sporophytes exposed to UVR are significantly lowered. Furthermore, morphological UV damage in Laminaria ochroleuca includes tissue deformation, lesion, blistering and thickening of the meristematic part of the lamina. The sensitivity of young sporophytes to DNA damage is correlated with thallus thickness and their optical characteristics. Growth rate is an integrative parameter of all physiological processes in juvenile plants. UV inhibition of growth may affect the upper distribution depth limit of adult life history stages. Juveniles possess several mechanisms to minimize UVR damage and, hence, are less sensitive but at the expense of growth. The species-specific susceptibility of the early life stages of macroalgae to UVR plays an important role for the determination of zonation patterns and probably also for shaping up community structure.
110 citations
TL;DR: The seasonal growth, reproduction, and occurrence of Chondrus crispus Stackhouse have been determined at four New Hampshire locations and correlated with seasonal and spatial variations of surface salinity, temperature, and nutrients.
102 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 2 |
| 2020 | 3 |
| 2019 | 2 |
| 2018 | 2 |
| 2017 | 2 |
| 2016 | 8 |