Drought Cycles Research Articles

Severe Biomass-Burning Aerosol Pollution during the 2019 Amazon Wildfire and Its Direct Radiative-Forcing Impact: A Space Perspective from MODIS Retrievals

An extreme biomass burning event occurred in the Amazonian rainforest from July through September 2019 due to the extensive wildfires used to clear the land, which allowed for more significant forest burning than previously occurred. In this study, we reclustered the clear-sky ambient aerosols to adapt the black carbon (BC) aerosol retrieval algorithm to Amazonia. This not only isolated the volumetric fraction of BC (fbc) from moderate-resolution imaging spectroradiometer (MODIS) aerosol data, but also facilitated the use of aerosol mixing and scattering models to estimate the absorption properties of smoke plumes. The retrieved MODIS aerosol dataset provided a space perspective on characterizing the aerosol changes and trends of the 2019 pollution event. A very high aerosol optical depth (AOD) was found to affect the source areas continuously, with higher and thus stronger aerosol absorption. These pollutants also affected the atmosphere downwind due to the transport of air masses. In addition, properties of aerosols emitted from the 2019 Amazonian wildfire events visualized a significant year-to-year enhancement, with the averaged AOD at 550 nm increased by 150%. A 200% increase in the aerosol-absorption optical depth (AAOD) at 550 nm was recognized due to the low single-scattering albedo (SSA) caused by the explosive BC emissions during the pollution peak. Further simulations of aerosol radiative forcing (ARF) showed that the biomass-burning aerosols emitted during the extreme Amazonian wildfires event in 2019 forced a significant change in the radiative balance, which not only produced greater heating of the atmospheric column through strong absorption of BC, but also reduced the radiation reaching the top-of-atmosphere (TOA) and surface level. The negative radiative forcing at the TOA and surface level, as well as the positive radiative forcing in the atmosphere, were elevated by ~30% across the whole of South America compared to 2018. These radiative effects of the absorbing aerosol could have the ability to accelerate the deterioration cycle of drought and fire over the Amazonian rainforest.

DROUGHT COPING STRATEGIES BY SMALLHOLDER CATTLE FARMERS IN ZIMBABWE

<p><strong>Background: </strong>The severity of drought in sub-Saharan Africa has led to crop failure and high mortalities of cattle. For decade’s drought-induced losses have been a persistent struggle for herded animals on rangelands. Persistent droughts have caused significant cattle losses, yet drought warning signs are not communicated in time to prepare farmers for adaptation and or mitigation. <strong>Objective: </strong>To analyse the adoption of drought coping strategies by smallholder beef farmers in Zaka District. <strong>Methodology:</strong> The sustainable livelihood framework guided the study in assessing the community adaptive strategies. Multi-stage cluster sampling method was employed and questionnaires were used to collect data. A chi-square test was used to evaluate the association between demographic characteristics and drought copping and mitigation strategies. A logit model and maximum likelihood estimation procedure was used to analyse the factors influencing adoption. <strong>Results: </strong>The results indicated that age and education status influenced (P < 0.05) drought copping strategies. Cattle disease and droughts were the major causes of cattle loses 38 and 35% respectively. Supplementary feeding, cattle disposal and lease grazing major were the adopted strategies. It was also found that farmer education level and access to agricultural training influenced adoption (P < 0.05). Cattle mortality, drought experience and crop losses are driving factors to adoption. Purchase of food items and its payment of medical bills are the major (P<0.05) reasons for selling beef cattle. <strong>Implications: </strong>Given the forecasts of future drought cycles, it is imperative that farmer’s establishment of drought feeding schemes, forage harvesting, investing in commercial protein supplements and communal breeding programs for drought-tolerant cattle be implemented. <strong>Conclusion: </strong>Cattle disposal, supplementary feeding and lease grazing are the adopted drought mitigatory strategies by beef communal farmers, yet these are only short term. Long term grazing strategies are recommended in order to reduce further cattle losses.</p>

Memory response of pepper antioxidant system to cycles of drought and re-watering stress

Memory response of pepper antioxidant system to cycles of drought and re-watering stress

Drought Assessment Based on Fused Satellite and Station Precipitation Data: An Example from the Chengbi River Basin, China

Drought poses a significant constraint on economic development. Drought assessment using the standardized precipitation index (SPI) uses only precipitation data, eliminating other redundant and complex calculation processes. However, the sparse stations in southwest China and the lack of information on actual precipitation measurements make drought assessment highly dependent on satellite precipitation data whose accuracy cannot be guaranteed. Fortunately, the Chengbi River Basin in Baise City is rich in station precipitation data. In this paper, based on the evaluation of the accuracy of IMERG precipitation data, geographically weighted regression (GWR), geographic difference analysis (GDA), and cumulative distribution function (CDF) are used to fuse station precipitation data and IMERG precipitation data, and finally, the fused precipitation data with the highest accuracy are selected to evaluate the drought situation. The results indicate that the accuracy of IMERG precipitation data needs to be improved, and the quality of CDF-fused precipitation data is higher than the other two. The drought analysis indicated that the Chengbi River Basin is in a cyclical drought and flood situation, and from October to December 2014, the SPI was basically between +1 and −1, showing a spatial pattern of slight flooding, normal conditions, and slight drought.

Stocking density and distribution in relation to vegetation in a biodiverse semi-arid pastoral system in South Africa

The spatial heterogeneity of vegetation in a communal grazing system provides pastoralists with a range of grazing sites to select for their livestock. When fencing spatially constrains herds, there is reduced access to ecological heterogeneity, which may have a negative impact on livestock and the grazing resource. This study investigated temporal and spatial changes in stocking densities and distribution within the six major vegetation types of the Leliefontein pastoral area in Namaqualand, South Africa. This semi-arid, biodiverse area of about 2000 km2 supports a spatially-constrained mobile pastoral system based on small stock production. Over the data period from 1999 to 2006, the location of 256 small stock herds, their temporal occupancy and herd size were used to determine stocking densities within the daily grazing radius of herds. These grazing radii were overlaid using GIS to produce stocking density distributions over the landscape. The density and location of herds were unevenly distributed when assessed monthly and annually. Parts of the study area were consistently overstocked whereas others remained ungrazed. We argue that the recommendation of fixed stocking rates within this variable environment is inappropriate because forage availability and quality fluctuate within and between years and within drought cycles. We conclude that development interventions should rather focus on reducing stocking densities during and after drought periods. This would benefit pastoralists through reduced livestock mortalities and the vegetation would recover more quickly from the impacts of drought.

Physiological and anatomical responses of Crambe abyssinica to repeated exposure to water deficit

Description of the subject. It is common for cultivated plants to face a single water deficit event, but in the wild plants are exposed to repeated cycles of drought and rehydration and the consequences of such repetitive events are less well understood. Objectives. The objective of this study was to understand how crambe’s performance under water limiting conditions is affected by previous exposure to water deficit. Method. Crambe plants were grown in 5.5 l pots and exposed to one (1WD) or three (3WD) water deficit cycles. As reference, plants were grown with daily irrigation. At the end of three water deficit cycles, the leaf anatomy, leaf relative water content (RWC), stomatal conductance, extravasation of electrolytes and chlorophyll fluorescence were analyzed. Results. Under water deficit, RWC significantly decreased in 1WD plants. However, in plants of the FMS CR 1307 lineage, the application of three water deficit cycles did not change the RWC and decreased the stomatal conductance and extravasation of electrolytes compared to the reference plants. Likewise, the kinetic difference in chlorophyll fluorescence (K-band and L-band) indicated improved stability and efficiency in utilizing energy. Conclusions. Our results show that the drought stress imposed three times induced adjustments in the physiology and anatomy of crambe plants. The FMS CR 1307 lineage was better able to store information from previous stressful events than the FMS Brilhante and FMS CR 1326 lineages, showing better performance under water deficit.

Drought Cycle Analysis to Evaluate the Influence of a Dense Network of Small Reservoirs on Drought Evolution

AbstractDrought‐affected regions often contain high densities of small reservoirs, usually informally built, as drought‐coping mechanism. These structures influence socio‐hydrological dynamics and have the potential to alter hydrological processes relevant to drought emergence and development. This study aimed to analyze the influence of a high concentration of small reservoirs on the intensification and evolution of drought events. We present an innovative method, which we call “Drought Cycle Analysis”, that tracks the concomitance of precipitation and water storage deficit and associates this with four drought stages: Wet Period, Meteorological drought, Hydro‐meteorological drought and Hydrological drought period. The methodology was tested for the Riacho do Sangue River watershed located in the semi‐arid region of northeast Brazil. We used a combination of satellite imagery (Landsat 5, 7 and 8) and an empirical equation to estimate the volume stored in the dense network of small reservoirs. Using the Drought Cycle Analysis, we show that the unmonitored small reservoirs induced and modified drought events, extending the duration of hydrological drought on average by 30%. Furthermore, this extension can double for specific drought events. The Drought Cycle Analysis method proved useful for monitoring and comparing the evolution of different drought events, in addition to being applicable as an auxiliary tool in the improvement of water resources management of large reservoirs. This study demonstrates the importance of considering small reservoirs in water resource management strategy development for drought‐prone regions.

Is Photoprotection of PSII One of the Key Mechanisms for Drought Tolerance in Maize?

Drought is one of the most important abiotic stress factors limiting maize production worldwide. The objective of this study was to investigate whether photoprotection of PSII was associated with the degree of drought tolerance and yield in three maize hybrids (30Y87, 31R88, P3939). To do this, three maize hybrids were subjected to three cycles of drought, and we measured the activities of photosystem II (PSII) and photosystem I (PSI). In a second field experiment, three maize hybrids were subjected to drought by withholding irrigation, and plant water status, yield and yield attributes were measured. Drought stress decreased leaf water potential (ΨL) in three maize hybrids, and this reduction was more pronounced in hybrid P3939 (−40%) compared to that of 30Y87 (−30%). Yield and yield attributes of three maize hybrids were adversely affected by drought. The number of kernels and 100-kernel weight was the highest in maize hybrid 30Y87 (−56%, −6%), whereas these were lowest in hybrid P3939 (−88%, −23%). Drought stress reduced the quantum yield of PSII [Y(II)], photochemical quenching (qP), electron transport rate through PSII [ETR(II)] and NPQ, except in P3939. Among the components of NPQ, drought increased the Y(NPQ) with concomitant decrease in Y(NO) only in P3939, whereas Y(NO) increased in drought-stressed plants of hybrid 30Y87 and 31R88. However, an increase in cyclic electron flow (CEF) around PSI and Y(NPQ) in P3939 might have protected the photosynthetic machinery but it did not translate in yield. However, drought-stressed plants of 30Y87 might have sufficiently downregulated PSII to match the energy consumption in downstream biochemical processes. Thus, changes in PSII and PSI activity and development of NPQ through CEF are physiological mechanisms to protect the photosynthetic apparatus, but an appropriate balance between these physiological processes is required, without which plant productivity may decline.

Differential Response of Two Tomato Genotypes, Wild Type cv. Ailsa Craig and Its ABA-Deficient Mutant flacca to Short-Termed Drought Cycles.

Two tomato genotypes with constitutively different ABA level, flacca mutant and wild type of Ailsa Craig cv. (WT), were subjected to three repeated drought cycles, with the aim to reveal the role of the abscisic acid (ABA) threshold in developing drought tolerance. Differential responses to drought of two genotypes were obtained: more pronounced stomatal closure, ABA biosynthesis and proline accumulation in WT compared to the mutant were compensated by dry weight accumulation accompanied by transient redox disbalance in flacca. Fourier-transform infrared (FTIR) spectra analysis of isolated cell wall material and morphological parameter measurements on tomato leaves indicated changes in dry weight accumulation and carbon re-allocation to cell wall constituents in flacca, but not in WT. A higher proportion of cellulose, pectin and lignin in isolated cell walls from flacca leaves further increased with repeated drought cycles. Different ABA-dependent stomatal closure between drought cycles implies that acquisition of stomatal sensitivity may be a part of stress memory mechanism developed under given conditions. The regulatory role of ABA in the cell wall restructuring and growth regulation under low leaf potential was discussed with emphasis on the beneficial effects of drought priming in developing differential defense strategies against drought.

Fruit Yield, Polyphenols, and Carotenoids in Long Shelf-Life Tomatoes in Response to Drought Stress and Rewatering

The Mediterranean long shelf-life tomato (or long storage tomato) is a plant traditionally cultivated under no irrigation in the Southern regions of Italy, whose fruits have typical high sensory and nutritional quality. However, yield levels are kept low under current cultivation conditions. In this study, the effects of repeated cycles of drying and rehydration on crop productivity and nutritional quality of fruits in terms of polyphenols and carotenoids content were assessed in long shelf-life tomatoes cultivated in a typical semi-arid area of Southern Italy. The three local Sicilian landraces ‘Custonaci’, ‘Salina’ and ‘Vulcano’, and the commercial tomato hybrid ‘Faino’ (control) were submitted to three irrigation treatments: DRY (no irrigation); IRR (long-season full irrigation); REW (drought/rewatering cycles). Total 450, 4710, and 1849 m3 ha−1, were distributed in DRY, IRR, and REW, respectively. At harvest, fruit yield, polyphenols (as total, flavonoids, and hydroxycinnamoyl quinic acids-HCQA), and carotenoids contents (lycopene and β-carotene) were measured. All cultivars benefitted from very limited irrigation in REW, raising their productivity (up to +147% in ‘Vulcano’) with respect to that of plants overstressed in DRY. Irrigation water use efficiency in REW was higher than that in IRR. Water shortage in REW led to a polyphenols content of fruits that was slightly lower (171.1 μg g−1) than that in DRY, but higher than that in IRR (116.8 μg g−1). All local landraces had greater contents (>160 μg g−1) than control (113.0 μg g−1). Under REW and DRY, the two landraces ‘Salina’ and ‘Vulcano’ produced fruits with the same polyphenols and flavonoids contents. Overall, the two water stressed treatments (DRY and REW) did not differ for HCQA content (>66 μg g−1), which was significantly higher than that in the irrigated plots (<50.55 μg g−1). Lycopene content in DRY and REW exceeded 100 μg g−1; among local types, ‘Vulcano’ exhibited the highest content (106.7 μg g−1). The β-carotene content did not change in ‘Custonaci’ and ‘Salina’, whereas in ‘Vulcano’ it was greater in DRY and REW. Only in ‘Faino’ water limitation in REW exerted a clear promoting effect on β-carotene content of fruits. The results of the present study reveal how rewatering after long-lasting drought periods is beneficial to long shelf-life tomatoes in terms of productivity. Appropriate drought cycles in REW may also help the fruits to retain high nutritional levels.

Groundwater Drought and Cycles in Xuchang City, China

The urban groundwater system is complex and affected by the interaction of natural and human factors. Groundwater scarcity can no longer reflect this complex situation, and the concept of groundwater drought can better interpret this situation. The groundwater drought cycle is the time interval in which groundwater droughts occur repeatedly and twice in a row. The study of the groundwater drought cycle can more comprehensively grasp the development characteristics of the groundwater drought, which is of great importance for the development, utilization, and protection of groundwater. This study used monthly observation data from seven groundwater wells in Xuchang, China, in the period 1980–2018. We applied the Kolmogorov–Smirnov test to select the best fitting distribution function and constructed a Standardized Groundwater Index (SGI). We analyzed groundwater drought at different time scales and used Morlet’s continuous complex wavelet transform to analyze the groundwater drought cycles. The following results were obtained: 1) the maximum intensity of groundwater drought in the seven observation wells ranged from 104.40 to 187.10. Well-3# has the most severe groundwater drought; 2) the drought years of well-5# were concentrated in 1984–1987 and 2003–2012 and those in the other wells in 1994–1999 and 2014–2018; and 3) the groundwater drought cycles in the seven observation wells were 97–120 months, and the average period is about 110 months. The cycle length had the following order: well-7# > well-4# > well-5# > well-2# > well-1# > well-3# > well-6. Therefore, Morlet wavelet transform analysis can be used to study the groundwater drought cycles and can be more intuitive in understanding the development of regional groundwater droughts. In addition, through the study of the Xuchang groundwater drought and its cycle, the groundwater drought in Xuchang city has been revealed, which can help local relevant departments to provide technical support and a scientific basis for the development, utilization, and protection of groundwater in the region.

Drought-Adaptive Mechanisms of Young Sweet Cherry Trees in Response to Withholding and Resuming Irrigation Cycles

The present work evaluates the main adaptive mechanisms developed by young sweet cherry trees (Prunus avium L.) to cope with drought. For this purpose, the young trees were subjected to two drought cycles with different water stress intensities followed by a recovery period. Three irrigation treatments were applied: control treatment (CTL) irrigated to ensure non-limiting soil water conditions; moderate water stress (MS) subjected to two drying cycles whose duration was dependent on the time elapsed until the trees reached values of midday stem water potential (Ψstem) of −1.3 and −1.7 MPa for the first and second cycle, respectively; and severe water stress (SS) similar to MS, but with reference values of −1.6 and −2.5 MPa. In-between drought cycles, MS and SS trees were irrigated daily as the CTL trees until reaching Ψstem values similar to those of CTL trees. The MS and SS trees showed an important stomatal regulation and lower vegetative growth. The decreasing leaf turgor potential (Ψturgor) during the drought periods accounted for 40–100% of the reduction in leaf water potential at midday (Ψmd). The minimum osmotic potential for mature leaves was about 0.35 MPa lower than in well-irrigated trees. The occasional osmotic adjustment observed in MS and SS trees was not sufficient to maintain Ψturgor values similar to the CTL trees or to increase the specific leaf weight (SLW). The leaf insertion angle increased as the water stress level increased. Severe water stress (Ψstem < −2.0 MPa) resulted in clear early defoliation as a further step in water conservation.

The heat wave of October 2020 in central South America

AbstractDuring September–November 2020, the meteorological services of Brazil, Argentina, Peru, Paraguay, and Bolivia reported record‐high maximum temperatures in several warm spells during this season. Positive and significant trends in heat wave frequency, intensity, and duration have been recorded since the 1980s, particularly in large cities. In this study, a heat wave is defined as a period in which both daily maximum and minimum air temperatures exceed the corresponding climatological 90th percentile for three or more consecutive days during September–November 2020. In this period, an intense heat wave during the first half of October and two heat waves events in November resulted in record‐breaking daily maximum temperatures in several locations in central South America. Places experienced temperature of about 10°C above normal, and some locations reported maximum temperatures above 40°C for several days in a row. Because its intensity and geographical extension, affecting central South America from southern Peruvian Amazon to southeastern Brazil, the heat wave of September 23–October 15 was selected as a case study. This intense heat wave was due a persistent atmospheric blocking located starting in late September and lasting until middle October 2020, a continuous presence of a warm air mass for several consecutive days contributed to pronounced positive temperature anomalies, possibly reinforced by extremely low soil moisture. This makes it easier for these high‐pressure systems to generate extreme heat waves because more of the sun's energy is going into heating the atmosphere rather than evaporating non‐existent water in the soil. This heat wave aggravated the drought over the Pantanal and other regions in October 2020, increasing fires and impacts on natural and human systems, representing a severe drought‐heat compound event. This vicious cycle of drought and extreme heat is of the kind expected under a warming climate.

Physiological Responses of Contrasting Maize (Zea mays L.) Hybrids to Repeated Drought

Maize is the most important crop worldwide in terms of production and yield, but every year a considerable amount of yield is lost due to drought. The foreseen increase in the number of drought spells due to climate change raises the question whether the ability to recover quickly after a water pulse may be a relevant trait for overall drought resistance. We here address the following hypotheses: (i) different maize hybrids exhibit distinct physiological adaptive responses to drought stress and (ii) these responses affect the ability to recover from the stress. (iii) The relative biomass production of maize hybrids, which show severe drought symptoms but are able to recover quickly after a water pulse, is comparable to those hybrids, which invest more energy into tolerance mechanisms. The physiological responses of eight maize hybrids to repeated drought were elucidated employing physiological parameters such as electrolyte leakage, osmolality, relative water content, growth rate and gas-exchange measurements. Only one hybrid was able to maintain biomass production under drought conditions. Amongst the others, two hybrids with similar growth inhibition but contrasting physiological responses were identified by a PCA analysis. Both strategies, i.e. stabilization of leaf water content via resistance mechanisms versus high recovery potential were equally effective in maintaining aboveground biomass production in the scenario of a long drought intermitted by a water-pulse. However, each strategy might be advantageous under different drought stress scenarios. Overall, the recovery potential is underestimated in drought resistance under natural conditions, which includes periodic cycles of drought and rewatering, and should be considered in screening trials.

Assessment of drought in SPI series using continuous wavelet analysis for Gediz Basin, Turkey

This study aims to estimate the short and long-term drought periodicities, and trend component using the continuous wavelet transforms. The applied approach introduces a new concept, the maxima line, which defines the most dominant component affecting the trend in Standardized Precipitation Index (SPI) time series. The analysis of the short and long-term drought cycles was performed with data from 15 stations located in Gediz Basin, at western part of Turkey, obtained during the recording period of 1960–2016. The change point in the SPI time series was determined graphically via the continuous wavelet power spectrum, and the obtained results were verified with Pettitt's test. The significant change points, in the northwest, east and southwest part of the basin, occurred by the beginning of 1980s, by the end of 1980s, and by the mid of 1990s, respectively. The most dominating periodicities affecting the trend were varying between 24 and 48 months for the short-term drought cycles, whereas they were varying between 96 and 162 months for the long-term drought cycles.

COVID-19, science and pseudoscience: a dangerous yin and yang

Today, science has allowed mankind to improve its survival rate and also, as never before in history, to improve health, sanitation, housing, communications, transportation, computing, entertainment, standard of living, etc. It is enough to look at what we have around us to realize that, thanks to science and technology, we use and use materials and devices that did not exist fifty years ago and are now indispensable for modern life. This slogan "Without science there is no future", so popular in times of the COVID-19 pandemic, has become famous, both in our country and in the world, and it would seem to be an obvious and redundant truth. However, we must be attentive to its proper management and technological applications, because they can literally have an impact on the life, death or welfare of people. The misuse of science in politics, scientific half-truths (the other half false or without proof) give momentary gains, but can have counterproductive consequences. We have many examples, such as the management and understanding of climate change in vulnerable countries like ours, which is often exposed to cycles of floods, landslides and droughts, with losses that can be avoided. There is also an impact on public health, as is the case with recurrent diseases such as malaria, dengue, chikungunya or zika, which are influenced by climate.

Analysis of historical drought and flood characteristics of Hengshui during the period 1649–2018: a typical city in North China

The objective of this study was to reconstruct the long-term drought and flood time series to analyze their changing characteristics in Hengshui City of North China. Disaster records of the city for 550 years (1649–2018) were collected from different sources and sorted to reconstruct the sequences of droughts and floods. Advanced statistical methods for climate data analysis, including the Mann-Kendall test, Sen's slope estimator, Morlet wavelet analysis, mutation point tests, and Rescaled range analysis, were used to analyze the historical changes and predict the direction of possible future changes in droughts and floods. The results showed an increased frequency of droughts and a decreased frequency of floods in Hengshui City, making drought occurrence significantly higher than flood occurrence in the twentieth century. The solar activity cycle of 11-year and its multiple showed the association with 10–15 years and 25 years cycles of droughts and floods, respectively. The mutation points in drought and flood sequences during 1559–1568 and 1909–1918 showed insignificant downward (upward) and upward (downward) trends, respectively, in the drought (flood) subsequence before and after the mutation point. The rescaled range analysis revealed an insignificant decreasing trend in droughts and the continuation of the present decreasing trend in floods in the forthcoming years.

Valorisation of Agri- and Aquaculture Residues via Biogas Production for Enhanced Industrial Application

Climate changes are nowadays reality and affect all aspects of everyday life. One of the places where these changes influence the society the most is the Brazilian Ceará region and Jaguaribara basin that suffer long-lasting, devastating drought cycles. They have a dramatic negative impact on local economy, forcing change in business models. This work presents the valorisation of wastes and residues from local fish, prawns, and the vegetable-cultivation industry via biogas production forced to adapt to these new circumstances. Along a single year, as much as 189.74 tonnes of wastes and residues can be processed by the biogas production facility, producing as much as 94 GJ of cooling energy and 1 tonne of biofertiliser monthly. Even for such a small biogas production facility, the NPV is positive already after 11 years; its IRR is 6.2%, and accumulated ROI for 20 years of operation is as high as 77.8%. This work demonstrates that a valorisation of industrial wastes and residues via biogas production is a feasible solution for a specific industrial scenario addressing new socio-economic challenges for the particular enterprise.

Dissolved organic nutrients at the interface of fresh and marine waters: flow regime changes, biogeochemical cascades and picocyanobacterial blooms—the example of Florida Bay, USA

The availability of dissolved inorganic and organic nutrients and their transformations along the fresh to marine continuum are being modified by various natural and anthropogenic activities and climate-related changes. Subtropical central and eastern Florida Bay, located at the southern end of the Florida peninsula, is classically considered to have inorganic nutrient conditions that are in higher-than-Redfield ratio proportions, and high levels of organic and chemically-reduced forms of nitrogen. However, salinity, pH and nutrients, both organic and inorganic, change with changes in freshwater flows to the bay. Here, using a time series of water quality and physico-chemical conditions from 2009 to 2019, the impacts of distinct changes in managed flow, drought, El Niño-related increases in precipitation, and intensive storms and hurricanes are explored with respect to changes in water quality and resulting ecosystem effects, with a focus on understanding why picocyanobacterial blooms formed when they did. Drought produced hyper-salinity conditions that were associated with a seagrass die-off. Years later, increases in precipitation resulting from intensive storms and a hurricane were associated with high loads of organic nutrients, and declines in pH, likely due to high organic acid input and decaying organic matter, collectively leading to physiologically favorable conditions for growth of the picocyanobacterium, Synechococcus spp. These conditions, including very high concentrations of NH4+, were likely inhibiting for seagrass recovery and for growth of competing phytoplankton or their grazers. Given projected future climate conditions, and anticipated cycles of drought and intensive storms, the likelihood of future seagrass die-offs and picocyanobacterial blooms is high.

Planting time optimization on tidal agricultural land

Tidal agricultural land (TAL) is a marginal farming field that is highly available but yet to be optimized in Indonesia. Productivity enhancement of TAL is achievable through agriculture technologies, but water management is the key solution to TAL main problems, i.e. flood and drought cycle. The main objective of this research was to predict tidal cycle for available planting time optimization in TAL. Research was conducted on 100 hectares TAL in Jejangkit, Barito Kuala, South Kalimantan, with the Alalak river become the main subject of the hydrodynamics monitoring. Watershed water balance simulation model run on 10-day interval was utilized to predict the tidal cycle with 4 input parameters including water-level, precipitation, percolation, and evapotranspiration. The prediction result showed that the available planting months in Jejangkit TAL was about 8 months, between the first or second 10-day of May and third 10-day of January or first 10-day of February (calibration and validation R2 were 0.78 and 0.92, respectively). On-field validation in Jejangkit recorded flood event started during the third 10-day of January 2020, which indicated that the prediction was reliable. This result shows that tidal cycle could be simulated using watershed water balance model to assist farmers on TAL’s productivity enhancement.