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Comparative ecophysiology of bloom-forming macroalgae in the Indian River Lagoon, Florida: Ulva lactuca, Hypnea musciformis, and Gracilaria tikvahiae

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... The photophysiological capacity of Ulva species is a key factor that determine their ability to form massive blooms (Cui et al., 2015;Wang et al., 2016;Huo et al., 2021), but it has mainly been characterized in temperate areas and subtropical estuaries, e.g., the Yellow sea, the southern coast of Brazil and Florida (Scherner et al., 2012;Xu et al., 2014;Whitehouse andLapointe, 2015, 2021). By contrast, the photophysiological response of Ulva species to face environmental stresses is not clearly defined in tropical and subtropical shallow coral reef lagoons. ...
... Photosynthesis irradiance curves have been used in the past to assess the effect of environmental factors on macroalgae physiology (Lapointe, 1981), including Ulva species (Figueroa et al., 2009;Scherner et al., 2012;Xu et al., 2014;Whitehouse and Lapointe, 2015;Wang et al., 2016). In this scenario, pulse amplitude modulated (PAM) fluorometry is a powerful and commonly used technique based on chlorophyll a fluorescence (Krause and Weis, 1991;Schreiber et al., 1994;Maxwell and Johnson, 2000). ...
... In this scenario, pulse amplitude modulated (PAM) fluorometry is a powerful and commonly used technique based on chlorophyll a fluorescence (Krause and Weis, 1991;Schreiber et al., 1994;Maxwell and Johnson, 2000). It offers the advantage to be fast (Schreiber et al., 1994) and is often used to assess photophysiological response of micro and macroalgae under stressful conditions (Figueroa et al., 1997(Figueroa et al., , 2009Scherner et al., 2012;Whitehouse and Lapointe, 2015;Coulombier et al., 2021). Although it has proven to be a useful and powerful tool for the studies of macroalgae photophysiology (Ralph and Gademann, 2005), this approach is often considered biased for macroalgae. ...
Article
To assess the photophysiological capacity of the recently described Ulva batuffolosa to form blooms in coral reefs, we monitored its biomass and photophysiological capacity with pulse amplitude modulated (PAM) fluorometry over a year period on a coastal barrier reef in New Caledonia, along with temperature and light. Effective and maximum quantum efficiencies of the photosystem II measured on this Ulva species indicated that the algae was in a “good health” all over the year with high quantum efficiencies under either light (Fq’/Fm’) or dark incubated conditions and (Fv/Fm). Photo-acclimation and -regulation status used by this Ulva sp. were driven by seasons (i.e., light and temperature) in the lagoon. Although photo-inhibition was an evidence during the warm period, U. batuffolosa was overall well adapted to tolerate the range of irradiance and temperature that characterized the lagoon over the year, which suggests that photosynthesis is not an impediment to green tides by this species.
... High biomass on beaches and coastal waters Lapointe (1995), Gower et al. (2006), Kopecky and Dunton (2006) High percent cover (in summer) Thom and Albright (1990) Grays Harbor, Washington Blidingia minima var. subsalsa/Ulva intestinalis complex High percent cover Thom (1984) Netarts (McGinty et al., 2002;Cole, 2002), the Indian River Lagoon in east-central Florida (Whitehouse and Lapointe, 2015), Tampa Bay (Hagan, 1969), embayments in southern California (McLaughlin et al., 2014), and the Salish Sea in Washington State (Frankenstein and Redman, 2000;Nelson et al., 2009). In these environments, Ulva forms thick mats that overgrow the benthos, resulting in hypoxia and anoxia, offensive odors, and loss of biodiversity. ...
... are common responders to sewage (Lapointe and O'Connell, 1989; and references therein). The frequency and magnitude of blooms of certain "ephemeral" C15 11/15/2017 17:9:21 Page 531 macroalgae such as Ulva lactuca have been considered as an indicator of high nutrient overenrichment, and seagrass success or failure Whitehouse and Lapointe, 2015). ...
... Macroalgae are often attached to benthic substrata (although many blooms can form drift populations) and therefore integrate nutrient availability at a given site over time scales of days to weeks. Opportunistic, fast-growing macroalgae can have rapid nutrient uptake rates, such as the red alga Gracilaria tikvahiae (D' Elia and DeBoer, 1978) and the green alga Ulva lactuca (Whitehouse and Lapointe, 2015). Accordingly, some macroalgae can be sampled to assess not only relative status of enrichment (nutrient quantity, and the internal tissue percentages of C, N, and P), but also the nutrient source(s) through stable isotope analysis (nitrogen [δ 15 N] and carbon [δ 13 C]) of tissues. ...
Chapter
Macroalgae are a natural, common feature of inland waters as well as estuaries, coastal waters, and oceanic waters particularly the Gulf of Mexico, North Atlantic Ocean, and Caribbean Sea where pelagic Sargassum is distributed. As the causes and effects of macroalgal blooms are similar in many ways to those associated with harmful phytoplankton species, scientists use the term harmful algal bloom (HAB) to describe this diverse array of bloom phenomena. Many studies have addressed the importance of nutrient loading to the development of macroalgal HAB. Unlike toxic phytoplankton blooms, macroalgal blooms usually lack direct chemical toxicity, but typically have a broader range of distribution and ecological impacts. Because of the negative environmental and economic impacts that are often associated with harmful macroalgal blooms, government agencies and private stakeholders have increasingly sought various strategies for management and mitigation, although the main historic approaches, physical removal and herbicide treatment, remain common.
... Many studies have evaluated the response of this macroalgae to the presence of different types of pollutants present in the surrounding environment (Bonanno et al., 2020;Diop et al., 2016;Ho, 1990;Ozyigit et al., 2017, among others). This specie presents a promising set of characteristics for environmental applications: it has a cosmopolitan distribution, high growth rates, withstanding high variations of water salinity, high rates of nutrient assimilation, especially ammonium (NH 4 + ), grows well in eutrophic waters and has tolerance to contaminants (Bonanno et al., 2020;Chen et al., 2015;Nielsen et al., 2012;Whitehouse and Lapointe, 2015). The differential nitrate and phosphate uptake and their storage are part of adaptive strategies evolved by macroalgae for their successful sustenance (Kumari et al., 2014). ...
... Eutrophication events, defined as an increase in nutrients, leading in excessive growth of plants such as phytoplankton or macroalgae, have economic and environmental effects in coastal shores around the world (Bat et al., 2001;Smetacek and Zingone, 2013). At high concentrations of N and P, the rapid growth and higher photosynthesis for U. lactuca have been attributed to its higher surface area:volume ratios compared with other macroalgae, such as H. musciformis or G. tikvahiae (Whitehouse and Lapointe, 2015). Furthermore, macroalgae such as U. lactuca, may reduce the occurrence of microalgae harmful blooms by reducing the nutrients available in the water columns (Tang and Gobler, 2011). ...
Article
Coastal regions are subjected to degradation due to anthropogenic pollution. Effluents loaded with variable concentrations of heavy metal, persistent organic pollutant, as well as nutrients are discharged in coastal areas leading to environmental degradation. In the past years, many scientists have studied, not only the effect of different contaminants on coastal ecosystems but also, they have searched for organisms tolerant to pollutants that can be used as bioindicators or for biomonitoring purposes. Furthermore, many researchers have demonstrated the capacity of different marine organisms to remove heavy metals and persistent organic pollutants, as well as to reduce nutrient concentration, which may lead to eutrophication. In this sense, Ulva lactuca, a green macroalgae commonly found in coastal areas, has been extensively studied for its capacity to accumulate pollutants; as a bioindicator; as well as for its remediation capacity. This paper aims to review the information published regarding the use of Ulva lactuca in environmental applications. The review was focused on those studies that analyse the role of this macroalga as a biomonitor or in bioremediation experiments.
... The maximum relative growth rate of H. flagelliformis (9% day −1 in Dec) in the present study was higher than other published data for the same genus (Faccini and Berchez 2000;Ganesan et al. 2006). Whitehouse and Lapointe (2015) concluded that the fastest growth rate of H. musciformis (0.35 doublings day −1 ) was in November. ...
... These findings of the current study are not consistent with those of Zarei Jeliani et al. (2017b), who found ammonium nitrogen had a significantly positive correlation with biomass production of Gracilariopsis persica. Some researchers have argued that high nutrient concentrations stimulate macroalgal growth rates (Whitehouse and Lapointe 2015;Zarei Jeliani et al. 2017b). Silkin et al. (2012) modeled nitrate and nitrite absorption by Gelidium latifolium and revealed the dependence of maximum content of nitrites in biomass on the initial nitrate concentration in the medium and depicted the positive correlation with the initial medium concentration of nitrite that reach to maximum (7 μmol g −1 ) in 80 μmol of nitrite concentration, while about nitrate, the maximum content of nitrate in biomass reaches to maximum amount (15 μmol g −1 ) in 20 μmol of nitrate concentration and then goes to steady state and shows no increase at higher concentration of nitrate. ...
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Global utilization of seaweeds for food, chemicals, pharmaceuticals, and production of polysaccharide is increasing and seaweeds are becoming the most important cultivated marine organisms. This study assessed the cultivation potential of the red alga, Hypnea flagelliformis, along the southern coastlines of Iran using monoline plastic rope method, with regard to several environmental parameters of seawater over a year (November 2017 to October 2018). Correlations between relative growth rate (RGR) and environmental parameters were investigated using Pearson correlation analysis. Biochemical composition contents (moisture, ash, protein, and lipid) of the cultivated samples were measured during the experiment. Yield and structural properties of the extracted carrageenan using aqueous and alkali-treated extraction of the samples were investigated using Fourier transform infrared (FT-IR) spectroscopy. This study showed that this species can grow only in 6 months of the year (November to April) in outdoor conditions. The highest relative growth rate (9 ± 0.4% day−1) was obtained in December. Salinity and temperature had significant impacts on the growth of H. flagelliformis. The biochemical composition content range for moisture (86.76-91.76% fw), ash (30-39% dw), total protein (1.40-3.03% dw), and lipid (1.08-3.15% dw) varied during the experiment. The yield of alkali-treated carrageenan (mean 34.5 ± 2.5% dw) was higher than aqueous method (mean 20.7 ± 1.3% dw). FT-IR analysis indicated that the extracted hydrocolloids are mainly from κ-carrageenan type. The findings demonstrate that H. flagelliformis has good potential for cultivation and as a carrageenan source.
... A shift of manatees to a predominantly macroalgal diet could have resulted in the inadvertent ingestion of toxic or pathogenic compounds. There is a diverse macroalgal population in the IRL, with Gracilaria tikvahiae, Hypnea musciformis, Acanthophora spicifera, Chaetomorpha sp., Ulva lactuca, and Codium decorticatum the major components of the drift algae that sometimes form high-biomass blooms under eutrophic conditions (Virnstein and Carbonara, 1985;Littler et al., 2008;Whitehouse and Lapointe, 2015;Barile, 2018). Qualitative gutcontent analysis of manatee carcasses examined during the UME revealed diverse macroalgae and seagrasses, paralleling the known availability of these forage items in the IRL following the major seagrass die-off of Thalassia testudinum, Halodule wrightii, and Syringodium filiforme triggered by superbloom events in 2012 (Morris et al., 2018). ...
Article
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The Indian River Lagoon (IRL) on Florida’s east coast is a biologically diverse estuary and an important habitat to the threatened Florida manatee (Trichechus manatus latirostris). An unusual mortality event (UME) was declared by the Working Group on Marine Mammal Unusual Mortality Events in 2013 after a marked increase in manatee deaths in the IRL of an unknown cause. This UME followed a dramatic reduction of seagrass coverage in the IRL due to chronic non-toxic phytoplankton blooms, with a resultant ecosystem shift to mixed macroalgal dominance. At least 199 manatee deaths fitting the UME case definition were documented in and adjacent to the IRL during 2012–2019; mortality was highest in 2013, when 111 of these deaths were documented. The case definition included carcasses in good nutritional condition, with multiorgan congestion or wet lungs consistent with drowning without trauma. The gastrointestinal compartments of manatee carcasses were filled with diverse macroalga species, and the contents were notably more fluid than usual. Gross intestinal findings included blebbing to segmental thickening of the wall. Microscopic lesions were primarily intestinal, including necrosis, edema, hemorrhage, mucosa-associated lymphoid changes, and inflammation, sometimes associated with Gram-positive bacterial rods. A multidisciplinary approach of environmental and carcass sampling found no causative evidence through tests for micro- and macroalgal biotoxins, trace metals, general toxin screening, or vitreum biochemistry. Microbiological, cytological, immunohistochemical, and molecular analyses of Clostridiales from intestinal samples identified Clostridioides difficile toxin A, toxins A/B and toxin A gene; Paeniclostridium sordellii lethal gene (and other potential virulence factors from a sequenced strain); and Clostridium perfringens alpha and epsilon toxin genes. The results from this 8 year-long investigation are indicative that the cause of death in this manatee UME was associated with clostridial infection, initiated by a shift to a predominantly macroalgal diet.
... Following the massive algae bloom, there have been recurrent blooms consisting of green macroalgae such as Chaetomorpha sp. since 2013 [4,5]. As a result of the 2011 super algal bloom, the coverage of seagrass within the IRL drastically declined from the loss of photosynthetic light by the surface algae [6]. ...
Article
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The Indian River Lagoon system (IRL), spanning ~40% of Florida's east coast, is one of the nation's biggest and most biodiverse estuaries. In 2011, a super algal bloom event occurred in the IRL with total nitrogen and phosphorus levels that exceeded historical levels. Scientists suspect that nonpoint source pollution through surface runoff may have had a significant impact on the recent recurring algal blooms. Digital Elevation Model, land cover/land use, and soil data were used to calculate a runoff coefficient for the IRL drainage basin. Rainfall data were used to calculate runoff depth for the study area between the years of 2006-2016. When the monthly runoff depth data for 2011 were compared to a previous study on the 2011 super algal bloom in the lagoon, areas with high runoff visually matched the areas with higher chlorophyll a concentrations. Land development was a significant variable for determining runoff depth (p < 0.0001), and although used to derive runoff depths, the influence of precipitation was marginally significant (p = 0.06). Significant spatial autocorrelation indicated local trends between land development and runoff depth (p < 0.0001). Outputs will aid with decisions on stormwater management to more sustainable land development planning.
... Asterisks indicate statistical significancy.et al., 2001; Shi and Wang, 2009; Hu et al., 2010;Whitehouse and Lapointe, 2015). ...
Article
The effects of temperature and irradiance on the growth of Ulva prolifera O.F. M{\ddot{u}ller (Chlorophyta), which has been used commercially as food in Korea, were examined in laboratory culture to conserve the strain. Experiments were conducted under combined factors of temperatures of 5, 10, 15, 20 and 25^{\circ}C and irradiances of 30, 50, 80 and 100µmol\;m^{-2}s^{-1}. The maximum growth of the U. prolifera germlings was observed at 20^{\circ}C and 80µmol\;m^{-2}s^{-1}, and the minimum growth was recorded at 5^{\circ}C and 100µmol\;m^{-2}s^{-1}. Considering these results, the species appears to survive under wide ranges of temperature and irradiance, although growth is inhibited by high irradiances of over 100µmol\;m^{-2}s^{-1}. This appears to be due to the in situ habitat niche of Ulva prolifera, which is the middle to lower intertidal zone. In conclusion, optimal conditions for the long-term conservation of Ulva prolifera can be established under relatively low temperatures (5^{\circ}C) and high irradiance (100µmol\;m^{-2}s^{-1}), while the optimal conditions for mass production are 20^{\circ}C and 80µmol\;m^{-2}s^{-1}.
... It is also known that changes in biomass could be attributed to seasonal changes, mainly in temperature, light intensity, water movement, tides and nutrients (Whitehouse and Lapointe, 2015). When these variables are appropriate, the release of propagules takes place; then when settlement occurs, they give rise to macroalgal blooms or "green tides". ...
... In this process, toxic species can release toxins which are fatal to fish, shellfish, mammals, and humans, while non-toxic phytoplankton species can accumulate to a higher biomass and result in hypoxia or anoxia (Stumpf and Tomlinson, 2005;Wells et al., 2015). In recent decades, both severity and intensity of HABs in lakes, reservoirs, rivers, and marine systems have increased as a consequence of climate change and anthropogenic disturbance (Masó and Garcés, 2006;Duan et al., 2009;Fu et al., 2012;Wells et al., 2015;Whitehouse and Lapointe, 2015). Nonetheless, the exact mechanism for the HABs is still not fully understood (Wells et al., 2015). ...
... Ulva blooms are seasonal phenomena where a large volume of coastal environment is taken over by Ulva biomass in a short period of time (Liu et al., 2010;Keesing et al., 2011). Among the abiotic factors that could trigger such events, the eutrophication of the estuarine environment can be considered as the main factor leading to the increasing number of blooms recorded worldwide (Smetacek and Zingone, 2013;Whitehouse and Lapointe, 2015). Here, we show a link between the nitrogen assimilation of Ulva strains and their growth, strengthening the causality between eutrophication and the occurrence of Ulva blooms. ...
... Ulva spp. also has a higher photosynthetic efficiency than other macroalgae species such as Gracilaria and Hypnea due to a higher ratio of surface area to volume reflected in its sheet-like structure (Whitehouse and Lapointe, 2015). Ulva species have a greater capability than other species to physiologically capitalize on the combination of higher temperatures, CO 2 enrichment and increased nitrogen loads anticipated due to climate change and ocean acidification (Parages et al., 2014;Chen et al., 2015). ...
Article
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Riverine nutrient loading from agriculture is one of the most prominent pressures in the second cycle of river basin management planning for the European Union (EU) Water Framework Directive (WFD). Better farmyard nutrient management planning is the measure most likely to reduce agricultural nutrient loading to catchment watercourses and coastal receiving waters. The adjoining Argideen Estuary and Courtmacsherry Bay in the south west of Ireland drain a 150 km2 catchment comprising mainly agricultural land. The receiving waters were allocated Poor ecological status under the WFD at the most recent appraisal. Sub-hourly water quality monitoring in the Timoleague River has been carried out by the Teagasc Agricultural Catchments Program to track the changes in nutrient loading to the Argideen Estuary in response to improved farming practice. A bio-physical model of the adjoining Argideen Estuary and Courtmacsherry Bay was calibrated subject to the prevailing climatic and nutrient loading regime. Six nutrient load scenarios were simulated to determine their impact upon macroalgae and phytoplankton bloom magnitude. In addition, nutrient flow-load relationships were derived for summers 2010 and 2016 to elucidate the improvements induced by better catchment management practice. Flow-load relationships for dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) for each year were applied to the flow data for the other year, to query the outcome if (1) there had been no change in farm management practice between 2010 and 2016, or (2) the improved farm management practice in place by 2016 had been implemented by 2010. The difference between expediting and delaying improvement in farm nutrient management practice was a 5% increase in DIN loading and a 233% increase in DIP load. Application of this higher estimated load to the calibrated bio-physical model projected an increase in 2016 Ulva bloom magnitude from 381t to 1,391t. Although phosphorus retention within the catchment has improved in recent years, with an attendant improvement in Ulva bloom magnitudes, flow connectivity in the catchment still facilitates a higher phosphorus transfer during large rainfall events. A high amount of phosphorus is stored within the catchment, while point source pressures continue to contribute to phosphorus transfer to streams during periods of low flow.
... As shown in results, Hypnea spinella and Filamentous red algae were relevant for the community of this region, positively correlated with minimum nitrate. Studies with Hypnea species, indicate that these algae can tolerate high nutrient concentration and act as biofilters of nitrogen and phosphorus (Martins et al., 2009;Ribeiro et al., 2013, Whitehouse andLapointe, 2015). Moreover, phosphate, which was correlated with nitrate ( Fig. S1), has a role in metabolic processes related to nitrate reductase activity, responsible to catalyze the reduction of nitrate to nitrite, which is an important factor in regulation of growth and protein production (Martins et al., 2009). ...
Article
Environmental conditions shape the occurrence and abundance of habitat-building organisms at global scales. Rhodolith beds structure important hard substrate habitats for a large number of marine benthic organisms. These organisms can benefit local biodiversity levels, but also compete with rhodoliths for essential resources. Therefore, understanding the factors shaping the distribution of rhodoliths and their associated communities along entire distributional ranges is of much relevance for conservational biology, particularly in the scope of future environmental changes. Here we predict suitable habitat areas and identify the main environmental drivers of rhodoliths’ variability and of associated epiphytes along a large-scale latitudinal gradient. Occurrence and abundance data were collected throughout the South-western Atlantic coast (SWA) and modelled against high resolution environmental predictors extracted from Bio-Oracle. The main drivers for rhodolith occurrence were light availability and temperature at the bottom of the ocean, while abundance was explained by nitrate, temperature and current velocity. Tropical regions showed the highest abundance of rhodoliths. No latitudinal pattern was detected in the variability of epiphytes abundance. However, significant differences were found between sampled sites regarding the composition of predominant taxa. The predictors influencing such differences were temperature and nitrate. The Tropical region is abundant in species with warm-water affinities, decreasing toward warm temperate region. The expressive occurrence of tropical species not referred before for warm temperate beds indicate a plausible tropicalization event.
... Following the massive algae bloom, there have been recurrent blooms consisting of green macroalgae such as Chaetomorpha sp. since 2013 [4,5]. As a result of the 2011 super algal bloom, the coverage of seagrass within the IRL drastically declined from the loss of photosynthetic light by the surface algae [6]. ...
... These conditions were amplified in recent years as a consequence of increased anthropogenic pressures (viz. industrial effluents, untreated sewage and agricultural runoff) resulting in increased frequency of occurrence and severity of blooms (Robin et al., 2013;Wells et al., 2015;Whitehouse and Lapointe, 2015;Fang et al., 2018). Nearly twenty-five diatom blooms have been reported from Indian waters since 1923 (Bhat and Matondkar, 2004;Padmakumar et al., 2007;D'Silva et al., 2012;Karthik et al., 2014). ...
Article
The role of allochthonous nutrient inputs in governing phytoplankton distribution and abundance were assessed from the estuarine regions of the Amba River, west coast of India. A total of 35 species belonging to 24 genera were recorded, where the diatom Coscinodiscus oculus-iridis (99%) dominated the estuarine mouth with a density of 3.5 × 10⁵ cells l⁻¹. Community analyses indicate that diversity (H’) decreased towards the estuarine mouth (0.002 ± 0.001) compared to the middle (0.38 ± 0.06) and inner estuary (1.83 ± 0.14) due to the diatom outbreak. Chlorophyll a reached an average of 12.51 μg l⁻¹ at the estuarine mouth, which is over three times the value determined in the middle estuary (4.25 μg l⁻¹). The key sources of these land-based nutrients are identified as agricultural land and urban runoff for nitrogen (N) and phosphorus (P), extensive sand mining for silica (Si) and aeolian deposition of iron minerals from industrial conveyor belts. A linear correlation between cell density and chlorophyll a with chemical variables indicated that silicate coupled with excess nitrogen input was crucial causative factors for the bloom. The nutrient enrichment towards the estuarine mouth is due to the dispersal of these land derived nutrients by complex hydrological forces.
... In this sense, many studies have evaluated the role of Ulva lactuca in relation with the presence of contaminants in the surrounding environment. This specie presents a promising set of characteristics for environmental applications; it has a cosmopolitan distribution, high growth rates, withstanding high variations of water salinity, high rates of nutrient assimilation, especially ammonium (NH4 + ), grows well in eutrophic waters and has tolerance to contaminants (Bonanno et al., 2020;Chen et al., 2015;Nielsen et al., 2012;Whitehouse and Lapointe, 2015). Moreover, it has a large surface area due to its thin and sheet-like thallus, and a relatively simple structure, with uniform and physiologically active cells that facilitates the interactions between the several functional groups in the surface and the metallic cations in solution (Sarı and Tuzen, 2008;Turner et al., 2007). ...
Chapter
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The Lactuca genus, which is characterized by a variety of forms including annual, biennial and perennial, glabrous or pubescent herbs with abundant latex, belongs to the Asteraceae family. Overall taxonomic literature has shown that 100-111 species represent the genus. The members are found primarily in warm and temperate regions mostly in the Northern Hemisphere. Among the all known species in the group of leafy vegetables, Lactuca sativa is considered as the most important vegetable. In many countries around the world, lettuce is cultivated commercially and is usually grown as a vegetable. The species is known for its high genetic diversity due to its polyphyletic origin and a complex cycle of domestication. Lettuce is the United States ' second most valuable crop and is a rich source of natural ingredients including ascorbic acid, vitamin A, vitamin K, β-carotene, lutein, and zeaxanthin. Besides, it is also regarded as a source of many minerals such as calcium, phosphorous, iron and copper. The Lactuca species are also essential sources of different phytochemicals and are used in traditional medicines for curing many ailments including inflammation, pain, stomach problems including indigestion and lack of appetite, bronchitis and urinary tract infections. The species show various pharmacological activities including antioxidant activity, anti-cancer activity, and antimicrobial activity and are also used for the treatment of neurodegenerative disorders. Lactucarium, a white milky compound isolated from wild lettuce (L. virosa), delivers similar effects as opium and is often referred to as “Opium lettuce” due to its pain-relieving activity. Aside from pain, the species is recommended as a natural treatment for a variety of disorders such as respiratory conditions, menstrual cramps, arthritis, cancer, insomnia, poor circulation, and urinary infections. Today there are number of wild lettuce products available in the market which contain extracts of plants leaves, seeds and milky sap and are considered beneficial for various human health disorders including anxiety, breathing issues, poor sleep, and joint pain.
... In this sense, many studies have evaluated the role of Ulva lactuca in relation with the presence of contaminants in the surrounding environment. This specie presents a promising set of characteristics for environmental applications; it has a cosmopolitan distribution, high growth rates, withstanding high variations of water salinity, high rates of nutrient assimilation, especially ammonium (NH4 + ), grows well in eutrophic waters and has tolerance to contaminants (Bonanno et al., 2020;Chen et al., 2015;Nielsen et al., 2012;Whitehouse and Lapointe, 2015). Moreover, it has a large surface area due to its thin and sheet-like thallus, and a relatively simple structure, with uniform and physiologically active cells that facilitates the interactions between the several functional groups in the surface and the metallic cations in solution (Sarı and Tuzen, 2008;Turner et al., 2007). ...
Chapter
Lactuca sativa, commonly known as lettuce, belongs to the Asteraceae family. It is used as both delicious vegetable and important folk medicine. It is low in carbohydrate and fat contents with high water contents. Lettuce is rich with minerals and vitamins including vitamin A,Lactuca sativa, commonly known as lettuce, belongs to the Asteraceae family. It is used as both delicious vegetable and important folk medicine. It is low in carbohydrate and fat contents with high water contents. Lettuce is rich with minerals and vitamins including vitamin A, C, E, iron, potassium, calcium and phosphorus. It also contains selenium which has medicinal properties for the prevention of colon, prostate and lung cancers. This chapter emphasizes the medicinal properties of lettuce and its active components for different biological actions, for example, anti-inflammatory, antioxidant, antidiabetic, antimicrobial, analgesic, sedative and neuroprotective effects. The therapeutic potential of this plant is primarily due to sesquiterpene lactones which are considered as the most active compounds of lettuce. These compounds impart health benefits by providing a balanced diet and by acting as therapeutic agents, due to their strong curative potential against heart and cancer diseases. Lettuce is also a rich source of phytochemicals and plant secondary metabolites. These phytochemicals in lettuce have been reported for analgesic, hypnotic, sedative and anticonvulsant properties. Dietary phytochemicals are of specific interest due to their significance as antioxidants. Later in the chapter, we have discussed different techniques that have been applied to identify phenolic and phytochemicals compounds in lettuce like liquid chromatography and mass spectrometry. A detailed primary and secondary metabolite profiling of lettuce has also been described. Because lettuce has strong medicinal potential, its utilization in dietary supplementation can be further investigated. Moreover, clinical studies are also needed to assess the efficiency and safety of lettuce preparations and its isolated compounds for the therapeutic application.
... In this sense, many studies have evaluated the role of Ulva lactuca in relation with the presence of contaminants in the surrounding environment. This specie presents a promising set of characteristics for environmental applications; it has a cosmopolitan distribution, high growth rates, withstanding high variations of water salinity, high rates of nutrient assimilation, especially ammonium (NH4 + ), grows well in eutrophic waters and has tolerance to contaminants (Bonanno et al., 2020;Chen et al., 2015;Nielsen et al., 2012;Whitehouse and Lapointe, 2015). Moreover, it has a large surface area due to its thin and sheet-like thallus, and a relatively simple structure, with uniform and physiologically active cells that facilitates the interactions between the several functional groups in the surface and the metallic cations in solution (Sarı and Tuzen, 2008;Turner et al., 2007). ...
Chapter
Lettuce (Lactuca sativa L.) is a worldwide vital leafy crop that is cultivated globally. As a result of the speedy progression of human population and their desire to grow, scientists have conducted many studies especially on the genetic transformation or genetic engineering of this plant. The main focus of the current lettuce cultivation programs is to improve horticultural as well as pharmacological characteristics of the plant such as enhancing quality, protection to early bolting, produce disease-free plants and production of important proteins of biopharming. These characteristics can be improved by genetic engineering as well as by adopting different transgenic approaches. The development of efficient and liable tissue culture methods is of prime importance for the successful accomplishment of the genetic transformation of the lettuce. Advances in micropropagation system and transformation methods have aided in increasing the transformation efficacy and constant expression of transgenes in lettuce. Although there is a lot of research that has been done on lettuce with the main purpose to produce pharmaceutically important proteins and vaccines, detailed comprehensive reviews on the basic transformation strategies and major regeneration system of lettuce plant are still missing. Moreover, chloroplast transformation offering unique benefits including high-level expression of foreign protein also needs to be considered. This chapter is focused on the genetic transformation of the lettuce including both nuclear as well as chloroplast transformation system along with major regeneration system and applications in plant biotechnology.
... and Ulva spp. have become more common (Whitehouse and Lapointe 2015). In our analyses, we used the average total percent cover of all seagrass species and the average percent occupancy of drift algae for a given transect on a given day (rather than the plot level data). ...
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Nutrient pollution, defined as excess nitrogen and phosphorus related to human activities, is a widespread anthropogenic impact that decreases water quality and limits light penetration in estuarine habitats. These factors can lead to shifts in primary producer communities, but the association between these changes and marine consumer patterns of abundance and growth is relatively unknown. Understanding these relationships is necessary for herbivorous species of conservation concern like the green turtle (Chelonia mydas). We used generalized additive models to analyze concurrent 18‐yr data sets of seagrass cover, drift macroalgae cover, juvenile green turtle abundance, and growth to (1) evaluate long‐term trends in primary producer cover and green turtle demographics; and (2) gain insights into their interrelatedness at a study site known to be affected by nutrient pollution throughout the study period. We found that seagrass cover sharply declined during our study period while macroalgae cover was more resilient with trends varying over time. Juvenile green turtle abundance slowly declined throughout the study period with altered intra‐annual trends, while growth rates remained relatively stable. The incongruence of these trends suggests that relationships between marine consumers and nutrient pollution are more complex than effects on food availability alone. Our results focus on the green turtle but highlight the need for greater understanding of relationships between marine consumer species and nutrient pollution at both local and regional scales.
... As demonstrated in other studies Ulva spp. are more competitive in nutrient rich waters where their growth rate is increased and also have higher surface-area to volume ratios compared to other species (Whitehouse and Lapointe, 2015). In subtropical waters around the world studies focus on the influence of anthropogenic activities on macroalgae blooms. ...
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Naturally-occurring pristine estuarine ecosystems are rare in modern environments due to anthropogenic encroachment. There are more than 100 outlets around the South African coast arising from streams flowing from small catchments close to the sea. Eight near natural systems were sampled seasonally over the period of a year to acquire baseline information on water quality and chlorophyll a status across a variety of algal guilds (benthic microalgae, phytoplankton and macroalgal cover). Albeit on a much smaller-scale, these systems represent natural surrogates of larger temporarily open/closed estuaries (TOCEs). Inorganic nutrients (ammonium, total oxidized nitrogen and soluble reactive phosphate), phytoplankton and microphytobenthos chlorophyll a, as well as macroagal percentage cover, were measured using standard methods. Algae showed a seasonal trend, with blooms of both micro- and macro-algae occurring during summer, with a dieback recorded in autumn. During summer, only one system had a phytoplankton peak in chlorophyll a above 20μgL-1, while the microphytobenthos concentrations in three of the systems were above 100mgm-2. Summer blooms of green filamentous macroalgae occurred in all four micro-outlets and in one micro-estuary. Using a linear mixed-effects modelling approach, significant drivers for algal growth related to temperature, nutrient conditions, light availability and water residence time, all of which are known to stimulate primary production. The results show that enrichment from natural sources display similar responses from primary producers to mesotrophic and/or eutrophic water bodies, with the exception that they revert to a natural state rather than continue into a degraded state as is the case in artificially enriched systems. This importantly demonstrates how larger temporarily/open closed estuaries, most of which are anthropogenically degraded, might have functioned under a former more balanced state. Some of these larger systems now respond to nutrient enrichment by exhibiting permanent cultural eutrophication.
Article
Global climate change has led to increased sea surface temperatures and altered precipitation patterns worldwide. Concurrently, macroalgal blooms in coastal systems have been increasing in frequency and severity globally and are successful due to their fast growth rates and broad environmental tolerances. Here, we examine the responses of the bloom-forming green algae Ulva compressa and U. lacinulata to individual and interactive effects of increased temperature and rain (divided into salinity and nitrogen effects). We assessed these impacts on the growth, photosynthetic efficiency, and tissue carbon and nitrogen content of both species. We found that temperatures ranging from 15–27 °C had no significant effect on the growth rate of either U. compressa or U. lacinulata, although both species tended to have lower growth rates after exposure to 27 °C for 3 weeks. High nitrogen, defined as a pulse of 60 µM NO3 and 20 µM NH4, enhanced the growth rate of U. compressa but not U. lacinulata and did not impact the photosynthetic efficiency of either species, although the C:N ratio revealed significant N limitation in both species. Lastly, we found the effects of temperature and rain (via added nitrogen) were not additive. Our results suggest that direct deposition of nitrogen via rain will enhance the growth of U. compressa, while increased temperatures likely will not. Together, our findings indicate that the prevalence of macroalgal blooms in coastal systems will likely increase under global climate change.
Technical Report
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This 2002 update is the second update of the Indian River Lagoon SWIM Plan which was first adopted by the state in 1989 in compliance with the 1987 SWIM Act (Chapter 373.451- 373.4595, F.S.). Considerable progress has been made since the last plan update, which was completed in 1994; but there is still much more work that should be done. This update documents the accomplishments, the current problems, and lays out a plan for future work. This document includes a status report on the state of the Lagoon, a summary of progress on projects undertaken since the last update, and recommendations for future projects and other actions over the next 5 years including major partnership programs. This document is organized by geographic region, beginning with a chapter offering a Lagoon-wide Overview (Chapter 2), followed by chapters on the major sub- lagoon watersheds: Mosquito Lagoon (Chapter 3), Banana River Lagoon (Chapter 4), North and Central IRL (Chapter 5), South IRL (Chapter 6), and St. Lucie River (Chapter 7). Within each chapter, the descriptions of resource status, issues, project objectives and progress, and planned activities are covered under the three major programs: Seagrass & Water Quality, Coastal Wetlands, and Public Involvement and Education. These three goals and programs have remained unchanged since they were first established for the development of the 1989 IRL SWIM Plan. Another program specific to the St. Lucie River generally complies with the three aforementioned goals, but has additional objectives related to the recovery of oyster habitat in the lower and middle reaches of the River and the enhancement of a fisheries nursery habitat in the River’s upper reach. The key performance indicators are the re- establishment of viable oyster habitat and submerged aquatic vegetation to their respective target levels. The Districts’ IRL and St. Lucie River programs are closely coordinated with several agency management plans and programs. Much of what has been accomplished in addressing the issues, goals and objectives of the IRL SWIM Plan during the past decade is due to the cooperation and efforts of many agencies -- local, regional, state, and federal. • Our understanding of the relationship between water quality and seagrass has advanced considerably, and thus, the factors that probably do or do not control seagrass distribution in the IRL system. • This understanding is an important pre-requisite for the development of final pollutant load reduction goals (or PLRGs), which can be viewed as “design criteria” for projects or strategies whose purpose is the improvement of water quality or clarity, the major Lagoon-wide factor influencing seagrass coverage. • Provisional water quality or pollutant load reduction targets have been established to enable the design of many non-point source projects to begin pollution abatement now rather than later. • There has been significant achievement in the control of point sources with the removal of more than 28 billion gallons of discharge from domestic wastewater treatment plants during the 7-year period from 1993 to 2000. • Nearly 56,000 acres of wetlands and uplands have been acquired for the purpose of constructing water quality remediation projects as well as for habitat preservation or rehabilitation. • More than a half-million cubic yards of harmful muck sediment deposits were removed from tributary creeks and canals; a precursor of more, larger scale muck removal projects in the future. There has been measurable improvement. • A net gain in seagrass coverage of nearly 4,000 acres has occurred from 1992 to 1999 (65,700 to 69,700 acres, respectively). The greatest gains in seagrass acreage are in areas that had experienced the greatest losses since 1943. It’s difficult to ascertain whether the improvement is primarily a result of restoration efforts or a response to weather patterns or other natural events. • There has been a noticeable increase in the public’s awareness of the Lagoon’s problems and its ecology, and the public’s understanding of the projects -- federal through local -- that benefit the Lagoon’s recovery and management. • More than 23,000 acres of impounded wetlands have been the hydrologically reconnected to the lagoon since 1989. Impoundment reconnections restore many of the estuarine functions provided by salt marsh and mangrove wetlands. The total acreage target is more than 37,000 acres. Future work on water quality and seagrass should be focused on non-point (stormwater) source controls in the Central and South IRL and in the St. Lucie River watershed To fully achieve the coastal wetland targets, especially in the North and Central IRL, land ownership and marsh management issues need to be resolved. Furthermore, the proper management of all reconnected impoundments is critical to the diversity and health of the IRL system. Descriptions and budgets of planned work over the next 5 years (2002/03 – 2006/07) are provided in some detail. Most of the planned work and projected annual budgets reflect the focus on priority needs mentioned above. Other important work is also planned and described. that can accelerate, enhance, or ensure restoration success. The plan for the next 5 years – the projects, and their schedules and budgets – is dependent on a relatively high level of federal, state, regional, and local cooperation, whether that cooperation is manifest as cost-share or as project collaboration collecting data or building structures. Success of the IRL programs will continue to be highly dependent on local government involvement – by cities, counties, mosquito control districts, and water control districts. Their collective involvement is typically demonstrated in the large amount of labor and equipment expended each year assisting the Districts in water quality and seagrass monitoring, reconnection and management of impounded coastal wetlands, land acquisition and management support, construction and maintenance of drainage treatment and erosion control systems, public education, and in many other activities. Participation by cities, counties, and water control districts will likely grow as they work to meet their responsibilities for achieving PLRGs and related resource targets, and wetland management targets.
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A massive bloom of the green macroalgae Ulva prolifera (previously known as Enteromorpha prolifera) occurred in June 2008 in the Yellow Sea (YS), resulting in perhaps the largest “green tide” event in history. Using a novel index (Floating Algae Index) and multiresolution remote sensing data from MODIS and Landsat, we show that U. prolifera patches appeared nearly every year between April and July 2000–2009 in the YS and/or East China Sea (ECS), which all originated from the nearshore Subei Bank. A finite volume numerical circulation model, driven by realistic forcing and boundary conditions, confirmed this finding. Analysis of meteorological/environmental data and information related to local aquaculture activities strongly supports the hypothesis that the recurrent U. prolifera in the YS and ECS resulted from aquaculture of the seaweed Porphyra yezoensis (or nori) conducted along the 200 km shoreline of the Subei Bank north of the Changjiang (Yangtze) River mouth. Given the continuous growth in aquaculture efforts in the region, similar macroalgae bloom events, such as the summer 2008 event, are likely to occur in the future, particularly between May and July. This was confirmed by the 2009 bloom event in the same regions and the same period. The profit of the local P. yezoensis aquaculture industry (∼16,000 Ha in 2007) is estimated as U.S. $53 million, yet the cost to manage the impact of the summer 2008 U. prolifera bloom exceeded U.S. $100 million. Therefore, better strategies are required to balance the economic benefit of seaweed aquaculture and the costs of environmental impacts.
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To investigate whether tissue N and P content of morphologically distinct macroalgae reflect different processes controlling nutrient availability, we measured water column nutrients and collected 5 species of algae for tissue N and P analysis from 18 stations along the southwestern coast of Puerto Rico. Nutrient content of sediments was also determined for a subset of stations. Southwestern Puerto Rico was chosen because the literature suggests that gradients in sediment type and organic matter content, advection, and terrestrial influence occur in this region, Stations were either inshore or offshore areas with 3 stations per area chosen a priori as High Nutrient Stations (HNS), Water column and sediment nutrient concentrations were elevated inshore and in HNS. Species were of 3 morphological forms: upright thalli with open branches, densely packed mats, and rhizophytic thalli. In the first category, Acanthophora spicifera had higher N content inshore compared to offshore while both A. spicifera and Hypnea musciformis had higher tissue N and P contents in HNS. In contrast, mat-forming algae (Dictyota dichotoma and D. cervicornis) had higher tissue N and P contents offshore compared to inshore. Although these species had high nutrients in many of the HNS, samples from some offshore reefs were equally high, Halimeda incrassata, a rhizophytic form, had greater tissue N content inshore than offshore, H. incrassata tissue nutrients were also elevated in some HNS, but not others. There were significant correlations between water column and sediment nutrients and the tissue N and P content of A. spicifera and H. incrassata, but not for either Dictyota. These results suggest algae with upright thalli and open-branching patterns may have a more direct relationship between tissue nutrient content and water column nutrient concentration than other forms. In contrast, mat-forming species may deplete nutrients within the mat, relying on strong currents found offshore to penetrate dense mats and replenish nutrients. Rhizophytic algae have access to both water column and sediment nutrients, and higher inshore tissue contents and at some HNS may reflect enhanced nutrient supplies from these sources. Our findings suggest that if other environmental factors are carefully taken into consideration, the tissue N and P content of macroalgae may prove to be an effective indicator of different nutrient sources in tropical systems.
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Rapid determination of which nutrients limit the primary production of macroalgae and seagrasses is vital for understanding the impacts of eutrophication on marine and freshwater ecosystems. However, current methods to assess nutrient limitation are often cumbersome and time consuming. For phytoplankton, a rapid method has been described based on short-term changes in chlorophyll fluorescence upon nutrient addition, also known as Nutrient-Induced Fluorescence Transients (NIFTs). Thus far, though, the NIFT technique was not well suited for macroalgae and seagrasses. We developed a new experimental setup so that the NIFT technique can be used to assess nutrient limitation of benthic macroalgae and seagrasses. We first tested the applicability of the technique on sea lettuce (Ulva lactuca) cultured in the laboratory on nutrient-enriched medium without either nitrogen or phosphorus. Addition of the limiting nutrient resulted in a characteristic change in the fluorescence signal, whereas addition of non-limiting nutrients did not yield a response. Next, we applied the NIFT technique to field samples of the encrusting fan-leaf alga Lobophora variegata, one of the key algal species often involved in the degradation of coral reef ecosystems. The results pointed at co-limitation of L. variegata by phosphorus and nitrogen, although it responded more strongly to phosphate than to nitrate and ammonium addition. For turtle grass (Thalassia testudinum) we found the opposite result, with a stronger NIFT response to nitrate and ammonium than to phosphate. Our extension of the NIFT technique offers an easy and fast method (30-60 min per sample) to determine nutrient limitation of macroalgae and seagrasses. We successfully applied this technique to macroalgae on coral reef ecosystems and to seagrass in a tropical inner bay, and foresee wider application to other aquatic plants, and to other marine and freshwater ecosystems.
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Field experiments demonstrate that the herbivorous marine snail Littorina littorea controls the abundance and type of algae in high intertidal tide pools in New England. Here the highest species diversity of algae occurs at intermediate Littorina densities. This unimodal relationship between algal species diversity and herbivore density occurs because the snail's preferred food is competitively dominant in tide pool habitats. Moderate grazing allows inferior algal species to persist and intense grazing eliminates most individuals and species. In contrast to pools, on emergent substrata where the preferred food is competitively inferior, this herbivore decreases algal diversity. Thus, the effect of this consumer on plant species diversity depends on the relationship between herbivore food preference and competitive abilities of the plants. These results may apply to most generalized consumers and provide a framework within which previously confusing results can be understood. Thus predators or herbivores d...
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Background: Rapid determination of which nutrients limit the primary production of macroalgae and seagrasses is vital for understanding the impacts of eutrophication on marine and freshwater ecosystems. However, current methods to assess nutrient limitation are often cumbersome and time consuming. For phytoplankton, a rapid method has been described based on short-term changes in chlorophyll fluorescence upon nutrient addition, also known as Nutrient-Induced Fluorescence Transients (NIFTs). Thus far, though, the NIFT technique was not well suited for macroalgae and seagrasses.
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Relationships between seaweed morphology and the metabolism of ammonium and carbon were examined for 9 seaweeds from northeastern New Zealand. Maximum rates of surge ammonium uptake and ammonium assimilation, in addition to the maximum ammonium storage pool, were strongly positively correlated with seaweed surface area:volume (SA:V) ratio when expressed per g dry weight, but were largely independent of SA:V ratio when expressed per cm2 surface area. This suggests that ammonium metabolism may be confined largely to the outermost cell layers. Similar scaling properties were found for rates of photosynthesis and, to a lesser extent, respiration. Rates of photosynthesis were similar to those derived from the literature for northern hemisphere seaweeds, while respiration rates were slightly lower among New Zealand seaweeds. These comparatively minor geographic differences suggest that previously documented differences in rates of ammonium uptake between the 2 regions are not related to carbon metabolism. Maximum rates of ammonium assimilation were determined by measuring the internally controlled rate of ammonium uptake, which closely matched the assimilation rate in the green seaweed Ulva sp., the red seaweed Osmundaria colensoi, and the brown seaweed Zonaria turneriana.
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Increased nutrient inputs to temperate coastal waters have led to increased occurrences of macroalgal blooms worldwide, To identify nutrients that are limiting to rnacroalgae and to determine whether different forms of these nutrients and long-term ambient nutrient conditions affect macroalgal response, we used in situ enrichment methods and tested the response of 2 bloom-forming species of macroalgae, Ulva lactuca and Gracilaria tikvahiae, from shallow estuaries of Waquoit Bay, Massachusetts, USA, that receive different land-derived N inputs. We enriched caged macroalgal fronds with nitrate, ammonium, phosphate, and N + P combinations, and measured growth, nutrient content, and delta N-15 signatures of fronds after 2 wk of incubation. In these estuaries, P did not limit. growth, however, the 2 species differed in growth response to N additions. Growth of U. lactuca was greater in Childs River (CR), the estuary with higher nitrate inputs, than in Sage Lot Pond (SLP); growth in SLP increased with nitrate and ammonium enrichment. In contrast, growth of G. tikvahiae was greater in SLP than in CR, but had no growth response to N enrichment in either site. C and N contents differed initially between species and sites, and after nutrient enrichment. Final tissue % N increased and C:N decreased after nitrate and ammonium enrichment. delta N-15 values of the rnacroalgae demonstrated uptake of the experimental fertilizers, and a higher affinity and faster turnover of internal N pools with ammonium than nitrate enrichment in both species. We suggest. that U, lactuca blooms in areas with both high nitrate and ammonium water column concentrations, and is more N-limited in oligotrophic waters where DIN levels are too low to sustain high growth rates. G. tikvahiae has a greater N storage capacity than U. lactuca, which may allow it to grow in less nutrient-rich waters.
Article
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We conducted a 3-factor nutrient-enrichment experiment (factors: N, P, initial tissue-nutrient status) on common species of macroalgae collected from 2 sites along SW Puerto Rico. Our objective was to determine the relative importance of N- or P-limitation among species and sites and to investigate the role of tissue-nutrient status in the response to increased nutrient supply. Acanthophora spicifera, Dictyota cervicornis, and Hypnea musciformis initially depleted in tissue nutrients responded strongly to either +N or +P alone and both nutrients together by increasing growth. In contrast, growth of these macroalgae with enriched internal stores of nutrients was generally not as nutrient-limited. In our 3 d experiments, the calcified alga Halimeda incrassata never showed a growth response, perhaps due to the short duration or adaptation to sediment nutrient supply. Tissue N-stores in all algae with low internal nutrient concentrations increased in response to +N, whereas initially higher N-stores were diluted to support growth during the experiment. In addition, all algae depleted the added N and P from the water over the course of the experiment, regardless of tissue-nutrient status. Depleted algae also took up dissolved organic nitrogen (DON) as a secondary source of N, either directly or after mineralization, whereas enriched algae may have 'leaked' NH4. Our results demonstrated that prior storage of nutrients strongly influenced the response of a number of tropical algal species to increased nutrient supply. This variable response to nutrients within and among algae from 3 major algal divisions over small geographical scales may partially explain the mixed results in previous studies of N- and P-limitation.
Article
Main effects and interactions of light and temperature on rates of nitrate (NO-3) uptake and levels of pigments and chemical constituents of the red seaweed Gracilaria tikvahiae were investigated in outdoor, nutrient-replete continuous-flow seawater culture chambers. Light intensity was the more important factor regulating levels of chlorophyll-a (Chl-a), R-phycoerythrin (R-PE) and %N all of which varied inversely with light. Temperature was the more important factor regulating levels of protein, carbohydrate, and %C, all of which varied inversely with temperature. High levels of C, N, protein and carbohydrate at 15°C suggest that G. tikvahiae either acclimates to low temperatures by increasing cellular levels of these constituents or accumulates these consituents at the reduced growth rates that occurred at this low temperature. Rates of NO-3-uptake by G. tikvahiae increased with increasing light and temperature up to the highest levels employed (i.e. I0, 30°C). A broad correlation between growth rate, photosynthetic capacity and NO-3-uptake by G. tikvahiae suggests that the ecological success of this alga may be due to its ability for highly balanced growth (i.e. proportional assimilation of C and N) over a broad range of light and temperature.
Article
Lapointe, B.E.; Herren, L.W., and Bedford, B.J., 2012. Effects of hurricanes, land use, and water management on nutrient and microbial pollution: St. Lucie Estuary, southeast Florida. Multiple hurricanes impacted southeast Florida during 2004 and 2005, producing record rainfall and large-scale stormwater runoff into the urbanized St. Lucie Estuary (SLE). To assess effects on water quality, field samples were taken in June and November 2005 and March 2006 along the SLE's three main segments: the South Fork, connected via the C-44 canal to Lake Okeechobee; the North Fork, which receives residential and agricultural runoff from the C-23 and C-24 canals; and the Middle Estuary, which flows into the Indian River Lagoon and Atlantic Ocean. Salinities were <1‰ throughout the normally brackish estuary during the 2005 samplings, but returned to near-normal levels by March 2006 in all but the South Fork. Low salinities in 2005 correlated with low dissolved oxygen, high turbidity, elevated nitrogen and phosphorus concentrations, and high fecal and total coliform counts. Highest turbidity (84.4 NTU), nitrate (37.9 μM), and total dissolved nitrogen (130.8 μM) concentrations occurred in the South Fork, whereas the highest ammonium (15.4 μM), soluble reactive phosphorus (10.5 μM), and total dissolved phosphorus (13.8 μM) concentrations occurred in the North Fork. High fecal and total coliform counts occurred in tidal creeks adjacent to dense residential areas that rely on septic tanks for on-site sewage disposal. The data suggest that increased stormwater retention, minimization of freshwater releases from Lake Okeechobee, and enhanced treatment of both stormwater and sewage are needed to mitigate future stormwater-driven water quality perturbations in the SLE.
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The definition of competition as the simultaneous use, by two or more individuals or species, of some limiting resource in short supply has recently received criticism. The author discusses the uniqueness of the individual thallus, intraspecific and interspecific competition and the implications for the community. Most benthic algae are exposed to a phylogenetically diverse array of consumers. -S.J.Yates
Article
The relationship between whole chain photosynthetic electron transport and PSII activity was investigated in Porphyra columbina (Montagne) (Rhodophyta), Ulva australis (Areschoug) (Chlorophyta), and Zonaria crenata ( J. Agardh) (Phaeophyta). Mass spectrometric measurements of gross O2 evolution and gross O2 uptake were combined with simultaneous measurement of pulse-modulated chl fluorescence under a range of irradiances and inorganic carbon (Ci) concentrations. At light-limiting irradiance, a good correlation between gross O2 evolution and the electron transport rate (ETR) calculated from chl fluorescence ((Fm′ - Fs)/Fm′) was found in the optically thin species (Ulva and Porphyra). The calculated ETR was equivalent to the theoretical electron requirement in these species but overestimated gross O2 evolution in the thicker species Zonaria. In saturating light, especially when Ci availability was low, ETR overestimated gross O2 evolution in all species. Excess electron flow could not be accounted for by an increase in gross O2 uptake; thus neither Mehler-ascorbate-peroxidase reaction nor the photosynthetic carbon oxidation cycle were enhanced at high irradiance or low C i. Alternative explanations for the loss of correlation include cyclic electron flow around PSII that may be engaged under these conditions or nonphotochemical energy quenching within PSII centers. The loss of correlation between ETR and linear photosynthetic electron flow as irradiance increased from limiting to saturating or at low Ci availability and in the case of optically thick thalli limits the application of this technique for measuring photosynthesis in macroalgae.
Article
Macroalgal blooms of Ulva lactuca and Hypnea musciformis have been problematic in shallow coastal waters around agricultural and urbanized regions of Maui, Hawai‘i for decades. Observations have highlighted the correspondence between these blooms and elevated nutrient levels from the adjacent land-use, however little evidence exists regarding the effects of nutrient enrichment on the blooming and non-blooming macroalgae in the area. To determine if elevated nutrient levels influence H. musciformis physiology, we conducted a nutrient enrichment (+N, +P, and +N+P) experiment and measured growth, photosynthetic status, and pigment absorbance. Phycobilin pigments were significantly reduced in the no addition and +P treatment and maintained in those with N additions, suggesting that H. musciformis can use phycobilins to store N. We conducted a second, larger experiment with additions of secondarily-treated wastewater effluent on the bloom forming species Acanthophora spicifera, H. musciformis, and U. lactuca and the common non-bloom forming species, Dictyota acutiloba. All samples were initially depleted of potential N stores and measured for growth, photosynthetic status, and N uptake rates; H. musciformis and U. lactuca were also assessed for micro nutrient uptake, % tissue N, and δ15N values. Growth rates of D. acutiloba, H. musciformis, and U. lactuca increased with increasing % wastewater effluent addition and concentrations of TN and NO3− and those of the bloom forming species were 2-fold higher. All species increased photosynthetic capacity and saturation irradiance with increasing % wastewater effluent addition and concentrations of TN and NO3−. U. lactuca was the most sensitive to low N conditions, evidenced by declines in light capturing efficiency. All species utilized a substantial amount of N over 24 h. H. musciformis and U. lactuca also (1) utilized micro nutrients: iron, manganese, molybdenum, and zinc, (2) decreased % tissue N in low N conditions, (3) increased % tissue N in response to elevated N conditions, and (4) expressed elevated δ15N values with increasing additions of wastewater effluent. These results demonstrate that in Hawai‘i, the bloom forming species H. musciformis and U. lactuca, have similar physiological responses to decreased and increased nutrient levels.
Article
Calcifying green macroalgae of the genus Halimeda are widely distributed on coral reefs and may become more abundant under higher nutrient availability. To determine how nutrient enrichment affects the physiological performance of Halimeda opuntia (Linnaeus) J.V.Lamouroux in relation to different water depths, we carried out in situ nutrient enrichment experiments in Curaçao, Netherlands Antilles. H. opuntia was collected in 5 m and then incubated at 5 and 15 m in clear acrylic cages with or without addition of N and P. Growth, algal tissue composition (internal C, N, and P content, δ15N signatures, protein content), photosynthetic performance and pigment content were measured after 14 days of incubation. Growth rates and total C increased with nutrients and were higher in 5 m water depth. N and P content were higher and δ15N signatures were lighter with nutrients in both depths. Photosynthetic performance, concentrations of the main and accessory photosynthetic pigments, and photoprotection also increased with nutrients and showed some response to depth. These results indicate that nutrient enrichment supported a rapid increase in physiological performance of H. opuntia, but with differences in depth. In 5 m, more C was allocated to growth, where light levels were sufficient, while in 15 m C was allocated to photosynthetic pigments. These results suggest that nutrient enrichment may influence their abundance and depth distribution on the reef.
Article
The effects of algal density, light adaptation, and interaction of light and nitrogen on nutrient uptake, growth, and biochemical composition of Ulva fasciata Delile were investigated in outdoor continuous cultures.With increasing plant densities, specific growth rates decreased exponentially from 0.36 to 0.02 doublings · day−1. In contrast, yields increased to a maximum of 4.7 g C · m−2 · day−1 at the intermediate density and then decreased.Plants grown under low (62 ly · day−1) and high (324 ly · day−1) light conditions were subsequently exposed to medium light (282 ly · day−1). Initially, plants from low light conditions had twice the chlorophyll a content and yield than plants from high light conditions. Within 1 wk, all plants showed no difference with regard to chlorophyll a and yield.Growth of U. fasciata did not saturate up to the highest light intensities used (255 ly · day−1). Nitrogen (NO3−) additions at low light did not affect growth but at high light there was increasing growth with increasing nitrogen. This interaction between light and nitrogen was apparent when growth was measured as specific growth rate (doublings · day−1), activity coefficient (mg C · g C−1 · day −1) and yield (g C · m−2 · day−1). These growth measures all significantly correlated with %C and ash content but not with %N, the C:N or C: Chl a ratios. Photosynthetic rate (g C · g Chl a−1 · day−1) showed no interaction between light and nitrogen because it corrected for increases in chlorophyll a content caused by nitrogen additions. This growth measure correlated with %N and the C: N and C: Chl a ratios as well as %C and ash content. Photosynthetic efficiency of U. fasciata was positively correlated with %N and chlorophyll a content and was affected by light intensity only at low nitrogen levels. Uptake of NO3− by U. fasciata depended mostly on the daily loadings of this nutrient, but was also inversely proportional to light intensity.
Article
Published data on mean annual epilimnetic total N (TN) and P (TP) were analyzed to find how TN : TP varies with lake trophic status. TN : TP is high in oligotrophic lakes and very low in eutrophic lakes, declining in a curvilinear fashion with increased TP. Comparison of this trend with published N : P in lake nutrient sources suggests that TN : TP reflects the source of nutrients: the ratio is high in oligotrophic lakes because they receive their N and P from natural, undisturbed watersheds which export much less P than N; mesotrophic and eutrophic lakes receive various mixtures of nutrient sources that have lower average N : P, and very eutrophic lakes have N : P that correspond very nearly to the N : P of sewage. Two inflection points were identified in the TN : TP relationship (-20 and - 100 wg TP liter-l) the first probably reflecting the large difference between TN : TP in nutrient export from undisturbed terrestrial ecosystems and that of meso- and eutrophic sources such as urban and pasture land runoff and sewage, and the second probably reflecting increased rates of denitrification in eutrophic lakes. Analysis of published manipulation experiments shows that N limitation is not only significantly more frequent in lakes of low ambient TN: TP (TN: TP mass ratio 5 14) but is also significantly more frequent in lakes with TP > 30 wg liter'.
Article
During the past two decades coral reefs in the greater Caribbean area have been altered by phase shifts away from corals and toward macroalgae or algal turfs. This study tested the hypothesis that because the phase shift on reefs in Jamaica and southeast Florida involved frondose macroalgae, bottom-up control via nutrient enrichment must be a causal factor. The approach was multifaceted and included measurement of near-bottom nutrient concen- trations, salinity, nutrient enrichment bioassays, alkaline phosphatase assays, tissue C : N : P ratios, and tissue 15N : 14N (6"N) ratios. In both locations, concentrations of dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) exceeded nutrient thresholds (- 1 .O PM DIN, 0.1 PM SRP) noted to sustain macroalgal blooms on Caribbean coral reefs. High seawater DIN : SRP ratios, alkaline phosphatase activity, and tissue C : P and N : P ratios of macroalgae on the carbonate-rich Jamaican reef suggested SRP limitation of productivity compared to lower values of these variables on siliciclastic reefs in Florida that suggested DIN limitation. This pattern was corroborated experimentally when SRP enrichment increased P,,,, (photosynthetic capacity at light saturation) of the chlorophyte Chaetomorpha Zinum in Jamaica compared to DIN enrichment that increased (x (the photosynthetic efficiency under low irradiance) of the deeper growing chlorophyte Codium isthmocladum in southeast Florida. Increased DIN concentrations were associated with reduced salinity on both reefs, indicating submarine groundwatcr discharge was a significant source of DIN. Elevated S15N values of C. isthmocladum tissue further pointed to wastewater DIN as a source of nitrogen contributing to the blooms in southeast Florida.
Article
Net and gross production rates were determined in the field at light intensities above 20,000 lux for 45 species of marine macroalgae from four different environments in southwestern North America. Thin sheetlike and finely branched thallus-forms showed greater rates than other forms. A morphological form more suited to efficiently utilize light energy and obtain nutrients is clearly related to the differences measured. There was a close relationship between dry weight as well as two-dimensional thallus area and photosynthetic performance for macrophytes having relatively large surface areas (i.e., thin and finely branched forms). However, the productivity values for the range of coarsely-branched to encrusting forms were in closer agreement with respect to thallus area than with respect to dry weight.
Article
Monthly collections of unattached, free-drifting macroalgae were made from September 1975 through August 1976 at three stations in a seagrass bed near Ft. Pierce, Florida. The most common species were Dictyota dichotoma, Acanthophora spicifera, Hypnea cervicornis, H. musciformis, and Spyridia filamentosa. Chondria tenuissima occurred as a winter-spring dominant. Seasonal changes in standing crop of these plants are described. Total algal biomass maxima occurred in spring and early fall when water temperatures ranged from 23 to 27 °C and light energy averaged 400 to 500 Langleys/day. Minimum total biomass occurred in summer. Frequency distributions of algal biomass were contagious in September and from January to May suggesting aggregated populations. Low randomness (p) values in the other months are suggestive of a regular distributional pattern. Problems involved in sampling this community are discussed and comparisons with other studies are presented.
Article
Macroalgal blooms of Hypnea musciformis and Ulvafasciata in coastal waters of Maui only occur in areas of substantial anthropogenic nutrient input, sources of which include wastewater effluent via injection wells, leaking cesspools and agricultural fertilizers. Algal δ15N signatures were used to map anthropogenic nitrogen through coastal surveys (island-wide and fine-scale) and algal deployments along nearshore and offshore gradients. Algal δ15N values of 9.8‰ and 2.0–3.5‰ in Waiehu and across the north-central coast, respectively, suggest that cesspool and agricultural nitrogen reached the respective adjacent coastlines. Effluent was detected in areas proximal to the Wastewater Reclamation Facilities (WWRF) operating Class V injection wells in Lahaina, Kihei and Kahului through elevated algal δ15N values (17.8–50.1‰). From 1997 to 2008, the three WWRFs injected an estimated total volume of 193 million cubic meters (51 billion gallons) of effluent with a nitrogen mass of 1.74 million kilograms (3.84 million pounds).
Article
Two species of macroscopic marine algae (Rhodophyceae) were grown and harvested continuously during 1974 in Fort Pierce, Florida. The seaweeds Gracilaria sp. and Hypnea musciformis were grown in both 600-l and 350-l tanks in the third stage of a nutrient removalaquaculture process that included microscopic marine algae and oysters in the first two stages. Mixtures of secondary-treated waste water and sea water constituted the initial nutrient source, with the seaweeds utilizing nutrients not assimilated by the microscopic algae and/or generated by the oysters. Standing crops of up to 7 900 g wet weight of Hypnea and 9 000 g Gracilaria were maintained. The Hypnea cultures could not be maintained in summer when tank temperatures reached 30°C, but Gracilaria grew during the entire year. On the basis of periodic harvesting, yields were consistently between 12 and 17 g dry weight per m2 per day for both species. These yields are as high as those achieved by mass cultures of microscopic marine algae, or by fast growing commercial crops such as sugar and rice.
Article
The slope of the initial linear range of a photosynthesis–irradiance (P–I) curve, alpha (α), is frequently, but often incorrectly, used to denote the maximal quantum yield (or the “efficiency” of photosynthesis) of higher plants and macroalgae under the conditions for which the P–I curve was measured. When using the increasingly popular method of pulse amplitude modulated (PAM) fluorometry, the determination of α from so-called rapid light curves (RLC) may lead to misinterpretations when comparing photosynthetic efficiencies under different environmental conditions. Furthermore, since PAM fluorometry measures the quantum yield (Y) directly, there may be no need to estimate it from the initial slopes of RLCs.We compared photosynthetic parameters derived from RLCs of Ulva sp. measured during winter and summer, and show large differences in α when electron transport rates (ETR) were plotted against incident irradiance (Ii) [α=0.26±0.00 versus 0.08±0.01 during the winter (November–December) and summer (July–August), respectively], as is usually done. On the other hand, no differences in the initial slopes of the RLCs were apparent when plotting ETR versus the absorbed irradiance (Ia) (initial slope=0.75±0.01 versus 0.62±0.12 during the winter and summer, respectively); this is called for since also ETR is calculated using Ia. Using the Ia based RLCs, it was also found that the values of the initial slopes equalled those of the first Y-value measurements of the RLCs (Y0) (t-test, p>0.05, r2=0.85). Therefore, when using PAM fluorometry, we suggest (a) to present the x-axis of RLCs as Ia (Ii×AF×0.5), and ETR on the y-axis as Y×Ia, and (b) that Y0 can be taken as a correct measure of the maximal quantum yield instead of estimating it from an RLC.
Article
Macroalgal blooms arc produced by nutrient enrichment of estuaries in which the sea floor lies within the photic zone. We review fcaturcs of macroalgal blooms pointed out in recent literature and summarize work done in the Waquoit Bay Land Margin Ecosystems Research project which suggests that nutrient loads, water residcncc times, presence of fringing salt marshes, and grazing affect macroalgal blooms. Increases in nitrogen supply raise macroalgal N uptake rates, N contents of tissues, photosynthesis-irradiance curves and P,,,.,, and accelerate growth of fronds. The resulting increase in macroalgal biomass is the macroalgal bloom, which can displace other estuarine producers, Fringing marshes and brief water residence impair the intensity of macroalgal blooms. Grazing pressure may control blooms of palatable macroalgac, but only at lower N loading rates. Macroalgal blooms end when growth of the phytoplankton attenuates irradiation reaching the bottom. In cstuarics with brief water rcsidencc times, phytoplankton may not have enough time to grow and shade macrophytcs. High phytoplankton division rates achieved at high nutrient concentrations may compensate for the brief time to divide before cells arc transported out of the estuary. Increased N loads and associated macroalgal blooms pervasively and fundamentally alter estuarinc ecosystems. Macroalgae intercept nutrients regenerated from sediments and thus uncoupIe biogeochemical sedimentary cycles from those in the water column. Macroalgae take up so much N that water quality seen:? high even where N loads are high. Macroalgal C moves more readily through microbial and consumer food webs than C derived from seagrasscs that were replaced by macroalgae. Macroalgae dominate 0, profiles of the water columns of shallow estuaries and thus alter the biogeochemistry of the sediments. Marc frequent hypoxia and habitat changes associated with macroalgal blooms also changes the abundance of bcnthic fauna in affected estuaries. Approaches to rcmediation of the many pervasive cffccts of macroalgal blooms riced to include interception of nutrients at their watcrshcd sources and perhaps removal by harvest of macroalgae or by increased flushing. Al- though we have much knowledge of macroalgal dynamics, all such management initiatives will require additional information.
Article
The effects of nitrogen species (formula omitted and formula omitted), loading (m moles of N/day) and seawater flow rate on the growth of the red seaweed Gracilaria foliifera var. angustissima (Harvey) Taylor were investigated in outdoor culture tanks. In one experiment, cultures received seawater enriched with either (formula omitted)secondarily treated wastewater (with N as (formula omitted) but the same daily nitrogen load at four seawater turnover rates (1,7.5, 15 and 30 culture volume ex-changes/day). In another experiment, cultures were maintained at four turnover rates (1,7.5, 15 and 30 culture volume exchanges/day) with (formula omitted) at a given concentration so that nitrogen loading was proportinal to turnover rate. Below 15 m moles of N/day, algal growth was N — limited and the plants had high C/N values and appeared bleached; above 15 m moles/day, the plants had C/N values of < 10 and were a dark brown color. Above this minimal daily N loading, algal growth was highly dependant upon flow rate per se. Yield of Gracilaria was greater with (formula omitted) than (formula omitted) at nitrogen loadings just adequate to support exponential growth; however, at higher levels of nitrogen loading the maximum recorded yields (up to 44 g dry weight/m2• day-1) occurred with (formula omitted) rather than (formula omitted). Water, ash and caloric content of Gracilaria was positively correlated with C/N values in N — limited plants. Absolute levels of both phycoerythrin and chorophyll increased proportionally with decreasing C/N values of the plants. Thus the observed nitrogen-related pigment changes in Gracilaria are light intensity and not necessarily light quality adaptaons.
Article
A series of outdoor, continuous-flow seawater cultures (50 l; 0.23 m2) were used to investigate the effects of culture density (kg/m2), nutrient loading (total nitrogen input/day) with both NH4+N and NO3−N, and turnover rate () on the growth and yield of Gracilaria tikvahiae. Although specific growth rates as high as 60% per day were recorded for Gracilaria at low densities (0.4 kg wet wt/m2) in summer conditions, maximum year-round yields were obtained at densities of 2.0–3.0 kg wet wt/m2. Above a minimal daily nitrogen loading the yield of Gracilaria was independent of (1) nutrient concentration, (2) nitrogen loading, or (3) whether nitrogen was in the form of NH4+N or NO3−N, but was (4) highly dependent upon flow rate. The time weighted mean annual production during 1976–1977 was 34.8 g dry wt/m2·day or 127 t/ha·yr based on 12-months continuous operation at near optimal densities and flow rates in the non-nutrient limited culture system.
Article
We examined the growth rate (µ) ofUlva lactuca L. (collected from Roskilde Fjord, Denmark in 1987) at different levels of dissolved inorganic carbon (DIC), pH and oxygen in two culture facilities. Growth was faster in Facility A (µ max ca 0.3 d−1) than in B (µ max ca 0.2 d−1), probably because of more efficient stirring and higher light intensity. The growth-DIC response curve exhibited low half-saturation constant (K 1/2) values (0.35 mM DIC in A, 0.55 mM in B) and growth rates close toµ max at natural seawater concentration of 2 mM DIC. Growth rate showed a low sensitivity to oxygen over a wide range of DIC and oxygen concentrations. Collectively, the results demonstrated an efficient mechanism for DIC use, unaffected by acclimatization to DIC concentrations between 0.2 and 3 mM. The growth rate decreased little between pH 7.5 and 9 at 2 mM DIC, but steeply above pH 9 approaching zero just above pH 10. The decline of growth at high pH may result from direct pH effects on cell pH, reduced HCO 3- availability and impaired operation of the carbon uptake process. The growth responses ofU. lactuca to DIC, pH and oxygen resembled those observed in previous short-term photosynthetic experiments. This similarity is probably due to the fast growth ofU. lactuca which means that photosynthetic products are rapidly converted into cell growth. Based on the culture experiments we argue that field plants ofU. lactuca not exposed to stagnant water and DIC depletion are likely to be limited in growth by environmental factors other than DIC (e.g. light and nutrients). Dense mats ofU. lactuca, however, may show reduced growth as a result of DIC depletion, high pH and self-shading.
Article
A new empirical equation is introduced that describes the photosynthesis by phytoplankton as a single, continuous function of available light from the initial linear response through the photoinhibited range at the highest levels liable to be encountered under any natural conditions. The properties of the curve are derived, and a procedure is given for fitting it to the results of light-saturation experiments for phytoplankton. The versatility of the equation is illustrated by data collected on natural phytoplankton assemblages from the eastern Canadian arctic and from the continental shelves of Nova Scotia and Peru.
Article
The seasonal cycle of biomass and tissue composition of Ulva rigida C. Agardh, in relation to nitrogen availability in the water column, was studied in 1991–1992 in the Sacca di Goro, a highly eutrophic lagoon in the Po River Delta (Italy). Nitrate uptake rates and storage capacity were also determined in laboratory experiments. The seasonal growth of U. rigida was related to the seasonal trend of nitrogen concentration in the water column. U. rigida biomass increased exponentially during spring and attained peaks of about 300–400 g dry mass (DM) m−2 in June. As biomass increased, U. rigida depleted nitrate in the water column. Thallus nitrate reserves also declined from 100 μmol N (g DM)−1 to almost undetectable levels, and total thallus nitrogen declined from 4% to 2.5% DM and 1.25% DM in 1991 and 1992, respectively. During summer, U. rigida decomposition increased, and organic nitrogen concentrations in the water column increased. The uptake experiments demonstrated an inverse relationship between thallus nitrate content and nitrate uptake rates. A modified Michaelis–Menten equation that accounts for thallus nitrate fit the uptake data well. U. rigida can accumulate up to about 400–500 μmol nitrate (g DM)−1 in cellular reserves. U. rigida in the Sacca di Goro has higher Km and lower Vmax/Km ratios for nitrate uptake than other chlorophycean species, indicating a low efficiency of uptake at low nitrate concentrations. This low uptake efficiency, and the ability to exploit N availability by storing cellular nitrate pools in excess of immediate growth needs, may represent a physiological response to an eutrophic environment where nitrate is in large supply for most of the year.
Article
Assessed relationships among total nitrogen (TN) and total phosphorus (TP) concentrations of the water column and the productivity, biomass, and epiphyte levels of Thalassia testudinum and Halodule wrightii along three onshore-offshore transects (Key West, Big Pine Key, and Long Key) stratified a priori into hypereutrophic (HYPER), eutrophic (EUTR), mesotrophic (MESO), and oligotrophic (OLIGO) communities with increasing distance from shore. H. wrightii was the dominant seagrass within inshore HYPER strata whereas T. testudinum was dominant at the EUTR, MESO and OLIGO strata. Seagrasses at the HYPER and EUTR strata had low shoot densities, low shoot production rates, slow areal biomass values, low areal production rates, but high levels of attached epiphytes and mat-forming macroalgae. Seagrasses at the OLIGO strata had the highest shoot densities, highest areal biomass values, highest areal production rates, and typically the lowest or second lowest epiphyte levels of all strata. Sustained nutrient enrichment from land-based activities results in increased biomass of attached epiphytes and macroalgae, which attenuate light, reduce dissolved oxygen, and lead to decline of T. testudinum and a gradient of habitat damage from nearshore to offshore waters. -from Authors
Article
Existing and new data were synthesized to analyze distribution patterns of seagrasses throughout the Indian River Lagoon complex from Ponce Inlet to Jupiter Inlet. Changes in abundance, distribution, and depth of occurrence between the 1940s and 1992 were evaluated. Potentially available habitat was estimated from bathymetric maps to estimate the extent of seagrass colonization of available habitat and the potential for increasing seagrass acreage by management programs. Seagrass abundance was estimated to be 11% less in 1992 than in the 1970s and 16% less than in 1986 for the entire complex. In particular, decreases in abundance appeared in the Indian River Lagoon north of Vero Beach. Evaluation of depth of occurrence indicated that the current (1992) maximum depth of seagrass beds is as much as 50% less than it was in 1943 in this portion of the Lagoon. Consistent decreases in depth were not found in Mosquito Lagoon, Banana River, or the Indian River Lagoon south of Ft. Pierce. Species composition patterns seem to follow patterns based on shallow water and salinity. Seagrass distribution in the lagoon may affect biodiversity patterns in other groups of plants and animals. Responses to short-term events and local water quality may also affect seagrass distribution. These factors must also be considered when assessing trends and in developing management strategies for the Indian River Lagoon. The Indian River Lagoon has the greatest seagrass diversity of any United States estuary, with a complex pattern of species assemblages that may depend on water clarity, salinity, temperature, or other factors. It is suggested that alteration of any of these, such as water clarity, may upset this diversity and balance of seagrass species in the Indian River Lagoon.
Article
Hypnea musciformis was collected during the summer and winter from a protected estuary and an exposed shore on the west coast of Florida. Apparent or net photosynthetic rates were recorded to determine optimal responses to light intensity, temperature, and salinity. The plants showed broad tolerances to all three factors with high rates of net oxygen production occurring between 15-35‰ salinity. Analysis of variance indicated significant differences in tolerance to light intensity and salinity, but not temperature between plants from the two sites and seasons. Responses of H. musciformis to forty-eight combinations of light intensity, temperature, and salinity were also conducted; the results suggest significant differences in synergistic effect between plants from the two sites. The photosynthetic rates of Hypnea can be used in predictive modeling which is necessary in mariculture.
Article
Pulse amplitude modulated (PAM) fluorometry can be used for measuring photosynthetic electron transport rates (ETR) of marine angiosperms and macroalgae both in the laboratory and in situ. Regarding macroalgae, quantitative values and linear correlations between ETR and rates of photosynthetic O2 evolution have so far been shown only for a few species under low irradiances. As a logical continuation of such work, the aim of the present study was to (a) assess to what degree high irradiances would limit such measurements and (b) evaluate whether PAM fluorometry could be used quantitatively also for other marine macroalgae from different phyla. This was done by comparing ETR with rates of gross O2 evolution (net O2 exhcange corrected for dark respiration) at various irradiances for the green alga Ulva lactuca grown at two irradiances, the brown algae Fucus serratus and Laminaria saccharina and the red algae Palmaria palmata and Porphyra umbilicalis. At low irradiances, there was a clear positive correlation between O2 evolution and fluorescence-based ETR. At high irradiances, however, all algae featured an apparent decrease in ETR while O2 evolution remained relatively constant, and this resulted in markedly increasing O2/ETR ratios. This anomaly could be nicely illustrated in plots of O2/ETR as a function of the effective quantum yield of photosystem II (Y). Such plots showed that the O2/ETR ratio generally started to increase when Y reached a critical low value of c. 0.1. It was further found that the irradiance at which this value was reached varied with species and previous light histories. Thus, it is the Y value, rather than the irradiance per se
Article
In this work, we attempt to quantify pulse amplitude modulated (PAM) chlorophyll fluorescence measurements in marine macroalgae in terms of photosynthetic rates. For this, the effective electron transfer quantum yield of photosystem II measured for two Ulva species, at various irradiances and inorganic carbon (Ci) concentrations, was multiplied by the estimated flux of photons absorbed by the photosynthetic pigments associated with this photosystem. The rates of electron transport (ETR) calculated in this way were then compared with rates of photosynthetic O2 evolution as measured in association with the fluorescence measurements. It was found that the calculated ETRs correlated linearly with rates of ‘gross’ O2 evolution (net O2 exchange corrected for dark respiration as measured immediately after turning off each irradiance level) within the range of irradiances applied (up to 608 µmol photons m−2s−1). The average molar O2/ETR ratio was 0.238 for Ulva lactuca and 0.261 for Ulva fasciata, which is close to the theoretical maximal value of 0.25. Rates of O2 evolution at various concentrations of Ci also showed linear correlations with ETR, and the average molar O2/ETR ratio was 0.249. These results show that PAM fluorometry can be used as a practical tool for quantifying photosynthetic rates at least under moderate irradiances in thin-bladed macroalgae such as Ulva possessing a CO2-concentrating system. A comparison between the PAM-101 (which was used in Sweden for the light- and Ci-response measurements of Ulva lactuca) and the newly developed portable Diving-PAM (used for Ulva fasciata in Israel) showed that such fluorescence-based photosynthetic rate measurements can also be carried out in situ.
Article
The presences of the common macroalgae Ulva sp. and Jania rubens vary between seasons along the Israeli Mediterranean intertidal zone. To reveal some of the potential acclimation mechanisms of these algae, we examined their photosynthetic traits during the year using rapid light curves (RLC) derived from pulse amplitude modulated (PAM) fluorometry. In addition, the relationships between those photosynthetic traits and the relative abundances of the two algae were investigated. Ulva sp. showed high maximal electron transport rates (ETRmax) (49.7–68.8 μmol electrons m−2 s−1) and onsets of light saturation values (Ek) (75.8–85.6 μmol photons m−2 s−1) in the winter months of December–February, while low values were found in the summer months of June–July (5.2–20.6 μmol electrons m−2 s−1 and 6.0–23.7 μmol photons m−2 s−1, respectively). At noon time (during the highest irradiance of the day), the maximal effective quantum yield (Y0) did not vary significantly during the year. These results indicate that seasonal irradiance influences the number of reaction centres per thallus area. Both algae showed depressions in Y0 at noon (23.8% for Ulva sp. and 20.3% for Jania rubens), indicating an efficient non-photochemical quenching mechanism. A positive correlation between the relative abundance and the photosynthetic parameter Y0 was found for Jania rubens when Y0 was sampled in the morning or noon, indicating that growth rate and primary production for this alga can be estimated from RLCs. No such correlation was found for Ulva sp., indicating that, in addition to photosynthetic traits, the relative seasonal abundance of this alga is influenced by other factors such as grazing and/or catastrophic events.
Article
The combined effects of light intensity and nitrogen (NO3−) on growth rate, pigment content, and biochemical composition of Gracilaria foliifera v. angustissima (Harvey) Taylor was investigated using outdoor continuous cultures. Growth of Gracilaria increased linearly with increasing light to 0.43 doublings d−1 at high light levels (383 ly d−1 of in situ light), suggesting that light may often limit growth of this plant in nature. Chlorophyll a and phycoerythrin contents were inversely proportional to light level and growth rate. However, pigment content did not affect the growth capacity of Gracilaria. There was no increase in growth or pigment content with increasing additions of nitrogen. The low nitrogen treatment was unenriched seawater that had higher NO3− levels than most coastal waters (influent = 8.61 μM; residual = 0.94 μM). When growing near its maximum rate under high light intensities, Gracilaria had a significantly (P < 0.001) lower phycoerythrin: chlorophyll a ratio (phyco: Chl a) than did Gracilaria growing more slowly under lower light (Phyco:Chl a of 2.8 ± 0.2 vs. 3.8 ± 0.3). Faster growing plants also had C:N ratios above 10, indicating N- limitation. In addition to harvesting light the phycobiliproteins of Gracilaria may store nitrogen. Growth rates of Gracilaria correlated negatively with ash (r =–0.85) and positively with the carbon: phycoerythrin ratio (r = 0.85), suggesting that these two indices can be used to estimate growth in the field.
Article
The relationship between whole chain photosynthetic electron transport and PSII activity was investigated in Porphyra columbina (Montagne) (Rhodophyta), Ulva australis (Areschoug) (Chlorophyta), and Zonaria crenata ( J. Agardh) (Phaeophyta). Mass spectrometric measurements of gross O2 evolution and gross O2 uptake were combined with simultaneous measurement of pulse-modulated chl fluorescence under a range of irradiances and inorganic carbon (Ci) concentrations. At light-limiting irradiance, a good correlation between gross O2 evolution and the electron transport rate (ETR) calculated from chl fluorescence ((Fm′− Fs)/Fm′) was found in the optically thin species (Ulva and Porphyra). The calculated ETR was equivalent to the theoretical electron requirement in these species but overestimated gross O2 evolution in the thicker species Zonaria. In saturating light, especially when Ci availability was low, ETR overestimated gross O2 evolution in all species. Excess electron flow could not be accounted for by an increase in gross O2 uptake; thus neither Mehler-ascorbate-peroxidase reaction nor the photosynthetic carbon oxidation cycle were enhanced at high irradiance or low C i. Alternative explanations for the loss of correlation include cyclic electron flow around PSII that may be engaged under these conditions or nonphotochemical energy quenching within PSII centers. The loss of correlation between ETR and linear photosynthetic electron flow as irradiance increased from limiting to saturating or at low Ci availability and in the case of optically thick thalli limits the application of this technique for measuring photosynthesis in macroalgae.
Article
Similar NH4+ and NO3−.uptake kinetic patterns were observed in Neoagardhiella baileyi (Harvey ex Kiitzing) Wyinne & Taylor and Gracilaria foliifera (Forssk?l) Borgesen. NO3− was taken up in a rate-sturating fashion described by the Michaelis-Menten equation. NH4+ uptake was multicomponent: a saturable component was accompanied by a diffusive or a high K component showing no evidence of saturation (at ≤50 μM [NH4+]). Nitrogen starved plantsi(C/N atom ratios > ca. 10) showed higher transient rates of NH4+ uptake at a given concentration than plants not N-Iimited. Only plants with high N content exhibited diel changes inNH4+ uptake rates, and showed transient rates of NH4+ accumulation which did not greatly exceed the capacity to incorporate N in steady-state growth. NH4+ was preferred over NO3−even in plants preconditioned on NO3−as the sole N. source, NO3− uptake was suppressed at 5μM [NH4+], but simultaneous uptake occurred at unsurpressed rates at lower concentrations. Potential for N accumulation was greater via NH4+uptake than via NO3−uptake. Changing capacity for NH4+ uptake with N content appears to be a mechanism whereby excessive accumulation of N was avoided by N-.satiated plants but a large accumulation was possible for N-depleted plants.