Chemical characterisation of Sargassum Inundation from the Turks and Caicos: seasonal and post stranding changes

The Turks and Caicos Islands (TCI) have been affected by sargassum inundations, with impacts on the economy and environment. Sargassum removal can be costly, but sargassum use and valorisation may generate income and offset environmental damage. A significant barrier to the valorisation of sargassum is insufficient knowledge of its chemical makeup, as well as its seasonal variation and decay after stranding. The chemical characterisation of mixed sargassum and its constituent species and morphotypes (S. natans I, S.natans VIII and S. fluitans) collected from TCI between September 2020 and May 2021 and changes in the composition of sargassum decaying (over 147 days) were studied. High ash (24.61–51.10% dry weight (DW)) and arsenic (49–217 mg kg−1) could severely hamper the use of this seaweed for food or feed purposes. Although there was some reduction in arsenic levels in decaying sargassum, levels remained high (>49 mg kg−1). Biomethane production by anaerobic digestion (AD) is a potential option. Nevertheless, the exploitation of sargassum for biogas, either fresh or as it decays on the beach, is challenging due to low methane yields (<42% of theoretical potential). Pre-treatment or co-digestion with other waste may be options to improve yield. The metal sorption ability of sargassum, which can be problematic, makes biosorption of pollutants an option for further research

Evidence for a subcortical origin of mirror movements after stroke: A longitudinal study

Following a stroke, mirror movements are unintended movements that appear in the non-paretic hand when the paretic hand voluntarily moves. Mirror movements have previously been linked to overactivation of sensorimotor areas in the non-lesioned hemisphere. In this study, we hypothesized that mirror movements might instead have a subcortical origin, and are the by-product of subcortical motor pathways upregulating their contributions to the paretic hand. To test this idea, we first characterized the time course of mirroring in 53 first-time stroke patients, and compared it to the time course of activities in sensorimotor areas of the lesioned and non-lesioned hemispheres (measured using functional MRI). Mirroring in the non-paretic hand was exaggerated early after stroke (Week 2), but progressively diminished over the year with a time course that parallelled individuation deficits in the paretic hand. We found no evidence of cortical overactivation that could explain the time course changes in behaviour, contrary to the cortical model of mirroring. Consistent with a subcortical origin of mirroring, we predicted that subcortical contributions should broadly recruit fingers in the non-paretic hand, reflecting the limited capacity of subcortical pathways in providing individuated finger control. We therefore characterized finger recruitment patterns in the non-paretic hand during mirroring. During mirroring, non-paretic fingers were broadly recruited, with mirrored forces in homologous fingers being only slightly larger (1.76 times) than those in non-homologous fingers. Throughout recovery, the pattern of finger recruitment during mirroring for patients looked like a scaled version of the corresponding control mirroring pattern, suggesting that the system that is responsible for mirroring in controls is upregulated after stroke. Together, our results suggest that post-stroke mirror movements in the non-paretic hand, like enslaved movements in the paretic hand, are caused by the upregulation of a bilaterally organized subcortical system

Rethinking interhemispheric imbalance as a target for stroke neurorehabilitation

© 2019 American Neurological Association Objective: Patients with chronic stroke have been shown to have failure to release interhemispheric inhibition (IHI) from the intact to the damaged hemisphere before movement execution (premovement IHI). This inhibitory imbalance was found to correlate with poor motor performance in the chronic stage after stroke and has since become a target for therapeutic interventions. The logic of this approach, however, implies that abnormal premovement IHI is causal to poor behavioral outcome and should therefore be present early after stroke when motor impairment is at its worst. To test this idea, in a longitudinal study, we investigated interhemispheric interactions by tracking patients’ premovement IHI for one year following stroke. Methods: We assessed premovement IHI and motor behavior five times over a 1-year period after ischemic stroke in 22 patients and 11 healthy participants. Results: We found that premovement IHI was normal during the acute/subacute period and only became abnormal at the chronic stage; specifically, release of IHI in movement preparation worsened as motor behavior improved. In addition, premovement IHI did not correlate with behavioral measures cross-sectionally, whereas the longitudinal emergence of abnormal premovement IHI from the acute to the chronic stage was inversely correlated with recovery of finger individuation. Interpretation: These results suggest that interhemispheric imbalance is not a cause of poor motor recovery, but instead might be the consequence of underlying recovery processes. These findings call into question the rehabilitation strategy of attempting to rebalance interhemispheric interactions in order to improve motor recovery after stroke. Ann Neurol 2019;85:502–513

Implications of resource management in La Parguera, Puerto Rico (The)

A recent rezoning of La Parguera, southwest Puerto Rico, as a tourist zone has resulted in an imbalance between development and appropriate resource management. Development associated with tourism is destroying the sub-tropical dry forest and adding pressure on the marine resources through increased boat traffic and marine structures. Declining water quality and benthic community health are two of the impacts seen in La Parguera associated with these land use changes. This study is three-fold. First, I evaluated the effect of houseboats on the benthic community. By comparing seagrass vigor under houseboats and in control areas, the houseboats were not found to be damaging seagrasses through shading nor were they reducing water quality. In fact, these boats may have positively impacted the localmarine system by creating an artificial reef environment. However, it was found that seagrass beds had significantly decreased in all areas since the last quantitative benthic study in 1979. Second, I examined the effect of land use changes on water quality. Declining water quality is a concern to the local townâs people who depend on the resource. Elevated chlorophyll-a concentrations indicated a source of nutrients entering near the waste treatment facility. Total suspended solids were significantly higher in reas near new development as compared to upstream and downstream sites (31.78 mg/l). Boat ramps were a point source for this material as well as trace metals. Third, I examined the distribution of seagrass beds near La Parguera. Seagrass beds were reduced or absent near development, and where they were found elevated epiphyte loads were associated with reduced productivity. Sediment composition was not significantly different in areas devoid of seagrasses, suggesting that seagrass might be able to recolonize if other impacts were reduced. Lower water quality and seagrass vigor in areas near recent development suggest that the changes in local zoning and lack of planning have measurably contributed to reduced water quality. Rapid changes in la nd use in La Parguera without consideration for best management techniques to control stormwater and nutrient runoff is causingdeterioration of water quality, and, in turn, deterioration of the benthic community of this marine system.Ph.D., Environmental Science and Engineering -- Drexel University, 200

An ecosystems perspective for food security in the Caribbean: Seagrass meadows in the Turks and Caicos Islands

Drawing attention to interactions between processes affecting biodiversity loss in marine environments and effects on food security, we draw on research in the Turks and Caicos Islands (TCI), a UK Overseas Territory in the Caribbean. Seagrass meadows provide ecosystem supporting services critical for human wellbeing. They are declining globally due to coastal development, poor land management, and destructive fishing practices. These systems are linked to traditional ways of life with multiple intangible values representing an important cultural resource for coastal communities. Using the lens of food security, we undertake interdisciplinary social–ecological research, to better understand the governance of ecosystem services and the food system in TCI. Research draws on mixed qualitative methods and data gathered via SeagrassWatch, fish surveys and meta-analysis of fish assemblages, revealing anthropogenic stressors exposing TCI to economic and environmental shocks characteristic of small island Caribbean states. We find growing concern regarding the islands׳ high dependence on food imports, coupled with declining availability of local fish and seafood across socio-economic groups. Weak governance structures put TCI׳s marine resources under increasing threat, with consequences for food security. We argue for the application of the precautionary principle, suggesting conservation actions through societal participation and stakeholder engagement

Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials

. After stroke, recovery of movement in proximal and distal upper extremity (UE) muscles appears to follow different time courses, suggesting differences in their neural substrates. . We sought to determine if presence or absence of motor evoked potentials (MEPs) differentially influences recovery of volitional contraction and strength in an arm muscle versus an intrinsic hand muscle. We also related MEP status to recovery of proximal and distal interjoint coordination and movement fractionation, as measured by the Fugl-Meyer Assessment (FMA). . In 45 subjects in the year following ischemic stroke, we tracked the relationship between corticospinal tract (CST) integrity and behavioral recovery in the biceps (BIC) and first dorsal interosseous (FDI) muscle. We used transcranial magnetic stimulation to probe CST integrity, indicated by MEPs, in BIC and FDI. We used electromyography, dynamometry, and UE FMA subscores to assess muscle-specific contraction, strength, and inter-joint coordination, respectively. . Presence of MEPs resulted in higher likelihood of muscle contraction, greater strength, and higher FMA scores. Without MEPs, BICs could more often volitionally contract, were less weak, and had steeper strength recovery curves than FDIs; in contrast, FMA recovery curves plateaued below normal levels for both the arm and hand. . There are shared and separate substrates for paretic UE recovery. CST integrity is necessary for interjoint coordination in both segments and for overall recovery. In its absence, alternative pathways may assist recovery of volitional contraction and strength, particularly in BIC. These findings suggest that more targeted approaches might be needed to optimize UE recovery