Temporal variations of Halodule wrightii meadows and associated fauna near their southern distribution limit in the southwestern Atlantic

2020 ◽  
Vol 63 (3) ◽  
pp. 215-228
Author(s):  
Laura Sordo ◽  
Paulo Lana
Keyword(s):  
Temporal Variations ◽  
Halodule Wrightii ◽  
Associated Fauna ◽  
Benthic Species ◽  
Southern Limit ◽  
Distribution Limit ◽  
Seagrass Biomass ◽  
Sw Atlantic ◽  
Number Of Leaves ◽  
Ecosystem Changes

AbstractHalodule wrightii meadows in Southern Brazil have been regressing in an unsheltered area of the subtropical Paranaguá Bay, near their southern limit in the SW Atlantic, since 2006. To identify early indicators of regression events, we assessed variations in plant and macrobenthic structure in two local meadows under unsheltered and protected conditions. Differences between sites increased after an epiphytic overgrowth of the alga Hincksia mitchelliae at the unsheltered site. Seagrass growth was suppressed and the numbers of burrowing and opportunistic benthic species increased with the increase of algal biomass. In the protected meadow, seagrass biomass and number of leaves changed seasonally, but macrobenthic abundance and species richness remained stable. Ecosystem changes were evident when the unsheltered meadow was already collapsing. The number of leaves per shoot, the horizontal internode length, the abundance and structure of the macrofaunal associations, and the host-epiphyte surface interactions, were the first variables to reflect the early stages of seagrass regression. Our results suggest that the persistence of H. wrightii meadows at their southern distribution limit in the SW Atlantic will be affected by local hydrodynamics and their ability to compete with ephemeral macroalgal species under stress conditions.

Temporal variations in morphology and biomass of vulnerable Halodule wrightii meadows at their southernmost distribution limit in the southwestern Atlantic

2011 ◽  
Vol 54 (1) ◽  
Author(s):  
Laura Sordo ◽  
Jérôme Fournier ◽  
Verônica M. de Oliveira ◽  
Fabiana Gern ◽  
Andrea de Castro Panizza ◽  
...  
Keyword(s):  
Temporal Variations ◽  
Halodule Wrightii ◽  
Southwestern Atlantic ◽  
Distribution Limit

scholarly journals Responses of the molluscan fauna to environmental variations in a Halodule wrightii Ascherson ecosystem from Northeastern Brazil

2013 ◽  
Vol 85 (4) ◽  
pp. 1397-1410 ◽  
Author(s):  
KCRISHNA V.S. BARROS ◽  
CRISTINA A. ROCHA-BARREIRA
Keyword(s):  
Seasonal Changes ◽  
Common Species ◽  
Temporal Variations ◽  
Northeastern Brazil ◽  
Halodule Wrightii ◽  
Hypnea Musciformis ◽  
Spatial And Temporal Distributions ◽  
Environmental Variations ◽  
Vertical Variations ◽  
Molluscan Fauna

ABSTRACT This study observed the spatial and temporal distributions of molluscs in a Halodule wrightii meadow, verifying if they respond satisfactorily to seasonal changes in this seagrass ecosystem. Twenty-four species were identified. Chitons were rare, bivalves had greater number of species (11), followed by gastropods (9) which were also the most abundant class (73%). All classes were more abundant in the belowground. The most common species was Tricolia affinis, especially in aboveground. The occurrence of some species in both strata or out of the expected stratum may have been influenced by shallow layer of the sediment considered in this study, hydrodynamic, and low biomass of the studied meadow. According to univariate and multivariate analyses, despite of molluscan descriptors had been related to variables associated with rainfall, the seagrasses had an important role on the seasonal and vertical variations of the molluscan fauna. The biomass of the epiphyte Hypnea musciformis was correlated to temporal variations of the species from aboveground, indicating its secondary role for this community. The molluscs were sensible to environmental variations, and also reflected seasonal changes of the seagrass, showing that damages on these meadows reflect even at lower levels of the marine food web.

Temporal variations in benthic assemblages

2009 ◽  
Author(s):  
John S. Gray ◽  
Michael Elliott
Keyword(s):  
Algal Blooms ◽  
Fish Larvae ◽  
Temporal Variations ◽  
Early Summer ◽  
Benthic Assemblages ◽  
Benthic Species ◽  
Resting Stages ◽  
North West ◽  
The Times ◽  
Planktonic Species

Most (but by no means all) benthic species have larval stages which use the water column for dispersal. As indicated in the previous chapter, a key process affecting recruitment to sediment systems is the need to disperse larvae in order to colonize new areas, even to the extent of releasing larvae at spring tides when the tidal excursion will be greatest, thus effecting an even greater dispersal. Seasonal release of larvae is the norm: most species develop gametes in spring and spawn in late spring or early summer (see Rasmussen 1973 for an excellent data set of the times of planktonic larval occurrence and settlement by many important north-west European boreal benthic species). Some species, however, avoid the high competition for food at this time and release gametes in autumn and winter. Thus larvae of benthic organisms are a key and often dominating component of the spring–summer plankton and play important roles as food for planktonic species such as fish larvae. Conversely, a number of planktonic species have resting stages in sediments. The most important of these are undoubtedly the diatoms and many flagellates, and also certain calanoid copepods such as Acartia, which are of course key components of the phytoplankton and zooplankton respectively. Diatom cysts are often found, and there is increased interest in the survival and hatching processes of dinoflagellate cysts that lead to harmful algal blooms. Similarly, the seasonal occurrence of many zooplankton species results from hatching of resting stages in the sediment (see Smetacek (1995), Boero et al. (1996), Pati et al. (1999) and Boero and Bonsdorff (2008) for reviews). The implication of many important planktonic species having benthic resting phases is that by predating cysts, benthic species may be able to control abundances of planktonic species. In this context the meiofauna are important predators (Pati et al. 1999). It is now important to consider the scales of temporal variation in benthic assemblages. First, seasonal changes occur in benthic assemblages of soft sediments even in the depths of the deep sea (e.g. Hsü and Thiede 1992). In spring, as light levels and temperature increase, a plankton bloom occurs.

Spatial-temporal variations of a SW Atlantic macrobenthic community affected by a chronic anthropogenic disturbance

2020 ◽  
Vol 156 ◽  
pp. 111189
Author(s):  
M.A. Saracho Bottero ◽  
M.L. Jaubet ◽  
E.N. Llanos ◽  
M.E. Becherucci ◽  
R. Elías ◽  
...  
Keyword(s):  
Anthropogenic Disturbance ◽  
Temporal Variations ◽  
Macrobenthic Community ◽  
Sw Atlantic

Effect of Spraying Foliar with Humus and Izomen Biostimulants on Some Vegetative and Flowering Parameters of Freesia hybrida L.

2019 ◽  
Vol 9 (2) ◽  
pp. 240-246
Author(s):  
Neveen Anwer Abdalla
Keyword(s):  
Plant Height ◽  
Landscape Design ◽  
Vase Life ◽  
College Of Agriculture ◽  
Flowering Date ◽  
Freesia Hybrida ◽  
Loam Soil ◽  
Number Of Leaves ◽  
The University

The experiment has been conducted in the nursery of the Department of Horticulture and Landscape Design, College of Agriculture, the University of Basrah to study the effect of Spraying foliar of the biostimulants Izomen and Humus on the growth and flowering of Freesia plants. The corms in similar size were planted in pots with a diameter and height of 25 cm, which filled with 2.5 kg of sterilized loam soil. After 50 days of planting, the plants sprayed with Humus at 0, 1.5, 2.5 ml L-1 and after five days sprayed with Izomen at 0, 1.5, 2.5 ml L-1 The different concentrations of biostimulants are sprayed three times, the period between one spray and another 15 is days. The results showed that the spraying of Humus at 2.5 ml L-1 significantly increased the plant height, the number of leaves and the leaf content of chlorophyll recorded (29.56 cm, 8.33 and 58.43%) respectively. Moreover, it is recorded early the flowering date (130 days), and the highest flowering mean is (2.12 inflorescence/plant) and the highest period of the remained flowers on the plant and the vase life (10 and 8 days) respectively. The effects of both Humus and Izomen were similar. In addition to the highest mean of their interaction at 2.5 ml L -1for all the studied traits.

Effect of rhizobacteria strains on the induction of resistance in barley genotypes against Cochliobolus sativus

2020 ◽  
Vol 13 (2) ◽  
pp. 83-92 ◽  
Author(s):  
A. Adam
Keyword(s):  
Plant Growth ◽  
Pseudomonas Putida ◽  
Growth Parameters ◽  
Disease Incidence ◽  
Dry Weight ◽  
Cochliobolus Sativus ◽  
Resistance Level ◽  
Wet Weight ◽  
Number Of Leaves ◽  
Barley Genotypes

SummaryEnhancement of the resistance level in plants by rhizobacteria has been proven in several pathosystems. This study investigated the ability of four rhizobacteria strains (Pseudomonas putida BTP1 and Bacillus subtilis Bs2500, Bs2504 and Bs2508) to promote the growth in three barley genotypes and protect them against Cochliobolus sativus. Our results demonstrated that all tested rhizobacteria strains had a protective effect on barley genotypes Arabi Abiad, Banteng and WI2291. However, P. putida BTP1 and B. subtilis Bs2508 strains were the most effective as they reduced disease incidence by 53 and 38% (mean effect), respectively. On the other hand, there were significant differences among the rhizobacteria-treated genotypes on plant growth parameters, such as wet weight, dry weight, plant height and number of leaves. Pseudomonas putida BTP1 strain was the most effective as it significantly increased plant growth by 15-32%. In addition, the susceptible genotypes Arabi Abiad and WI2291 were the most responsive to rhizobacteria. This means that these genotypes have a high potential for increase of their resistance against the pathogen and enhancement of plant growth after the application of rhizobacteria. Consequently, barley seed treatment with the tested rhizobacteria could be considered as an effective biocontrol method against C. sativus.

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