Linda J. Walters

Dextral Pan‐African Shear Along the Southwestern Edge of the Achankovil Shear Belt, South India: Constraints on Gondwana Reconstructions

The Achankovil shear belt of the southern Indian Peninsular shield is prominent on Landsat images. It coincides with the boundary between charnockites of the Madurai block to the north and khondalites of the Trivandrum block to the south, and with a major change in the aeromagnetic pattern that can be traced across southern India. Field investigations reveal a major shear zone along the southwestern edge of the Achankovil shear belt, the Tenmala shear zone. Rocks in the Tenmala shear zone include charnockite, garnet‐biotite gneiss, garnet‐sillimanite gneiss, cordierite gneiss, and granite. Kinematic indicators include stretched and asymmetric garnet, feldspar and quartz porphyroclasts, shear bands, asymmetric folds, extensional and contractional composite structures, hook folds on rotated and deformed gash veins, and lineations. Kinematic analysis of these features along 60 km of the shear zone indicates primarily dextral shear, with a minor component of reverse shear. Textures, as well as mineral assemblages, are consistent with deformation under granulite facies conditions. Some overprint by the most recently formed charnockite postdates the shearing. Limited geochronologic data suggest a late Proterozoic (Pan‐African) age of shearing. Dextral shear along the Achankovil shear belt is opposite to the sinistral shear reported for the Bongolava‐Ranotsara shear zone in southerhem Magascar; hence these two shear zones cannot be correlated in reconstructions of these parts of Gondwana.

A forensic and phylogenetic survey of Caulerpa species (Caulerpales, Chlorophyta) from the Florida coast, local aquarium shops, and e-commerce: establishing a proactive baseline for early detection.

Baseline genotypes were established for 256 individuals of Caulerpa collected from 27 field locations in Florida (including the Keys), the Bahamas, US Virgin Islands, and Honduras, nearly doubling the number of available GenBank sequences. On the basis of sequences from the nuclear rDNA‐ITS 1+2 and the chloroplast tufA regions, the phylogeny of Caulerpa was reassessed and the presence of invasive strains was determined. Surveys in central Florida and southern California of >100 saltwater aquarium shops and 90 internet sites revealed that >50% sold Caulerpa. Of the 14 Caulerpa species encountered, Caulerpa racemosa was the most common, followed by Caulerpa sertularioides, Caulerpa prolifera, Caulerpa mexicana, and Caulerpa serrulata. None of the >180 field‐collected individuals (representing 13 species) was the invasive strain of Caulerpa taxifolia or C. racemosa. With one exception (a sample of C. racemosa from a shop in southern California belonged to the invasive Clade III strain), no invasive strains were found in saltwater aquarium stores in Florida or on any of the internet sites. Although these results are encouraging, we recommend a ban on the sale of all Caulerpa species (including “live rock”) because: morphological identification of Caulerpa species is unreliable (>12% misidentification rate) and invasive strains can only be identified by their aligned DNA sequences, and because the potential capacity for invasive behavior in other Caulerpa species is far from clear. The addition of the Florida region to the genetic data base for Caulerpa provides a valuable proactive resource for invasion biologists as well as researchers interested in the evolution and speciation of Caulerpa.

Field biology of Halimeda tuna (Bryopsidales, Chlorophyta) across a depth gradient: comparative growth, survivorship, recruitment, and reproduction

Growth, survivorship, recruitment, and reproduction of Halimeda tuna, a dominant green alga in many reef systems of the Florida Keys, were monitored at a shallow back reef (4–7m) and deep reef slope (15–22 m) on Conch Reef. Despite lower light intensities and similar grazing pressures, amphipod infestations, and epiphyte loads at both sites, the deeper site exhibited significantly higher growth rates in summer months over a 4-year period than found for the shallow population, possibly because of higher nutrient levels at depth and photoinhibition of shallow plants. Sexual reproductive events occurred simultaneously across the entire reef, with up to 5% of the population at both sites developing gametangia. New upright axes formed from zygotes, asexual fragmentation, or vegetative runners. Plants appear to have persistent basal stumps that survive harsh environmental conditions, even if upright, photosynthetic axes are removed. Sexual reproduction and ‘smothering’ by epiphyte overgrowth are hypothesized to be two causes of death for individuals.

Asexual propagation in the coral reef macroalga Halimeda (Chlorophyta, Bryopsidales): production, dispersal and attachment of small fragments

Siphonous, green macroalgae of the genus Halimeda are ubiquitous and ecologically important in tropical and subtropical marine environments. It has been hypothesized that the abundance of Halimeda on coral reefs is in part due to the ability of this genus to propagate asexually via vegetative fragmentation. However, vegetative fragmentation has only been documented for H. discoidea in a laboratory setting. To test the hypothesis that vegetative fragmentation contributes to field populations of Halimeda, we examined three aspects of fragmentation by H. tuna (Ellis and Solander) Lamouroux, H. opuntia (Linneaus) Lamouroux and H. goreaui Taylor on Conch Reef in the Florida Keys: (1) short-term (8 days) and long-term (14 weeks) fragment survival and rhizoid production in the laboratory and field (7 and 2 1 in), (2) size of the fragment pool and (3) influences of herbivory and water motion on production and dispersal of fragments. Although morphologically similar to H. discoidea, only a small percentage of H. tuna fragments survived. Fragments of H. opuntia and H. goreaui were more robust, and survival and rhizoid production were positively correlated with size in short-term trials. In 14-week field trials, one-third or fewer fragments of any species survived at 7 m, potentially because fragments were covered by large amounts of sediment. Survivors included some buried, seemingly dead individuals that turned green when exposed to light, highlighting the remarkable ability of this genus to survive disturbances. There was much. less sediment accumulation at 21 m, where more fragments survived. Most (93%) eight-segment fragments of H. opuntia produced attachment rhizoids by the end of the 14-week trial. Overall, a range of 4.7-9.4 fragments of Halimeda m(-2) day(-1) were found on Conch Reef, most fragments were generated by H. goreaui. Fish bite marks were evident on 75-85% of the individuals of H. tuna and the number of bites per thallus ranged from 1 to 23. Herbivorous reef fish commonly fed on all three species of Halimeda. Some fish consumed the biomass, while others rejected most bites. For example, 83% of bites were rejected by the blue-striped grunt. Dispersal distances for rejected bites ranged from 0 to 31 m. Water motion was also responsible for fragment dispersal; experimentally produced fragments moved up to 48 cut day(-1). Results presented here suggest that asexual propagation of fragments of Halimeda is an important component of the life-history of this genus and vegetative fragmentation contributes to the abundance of this genus on coral reefs

E‐commerce and Caulerpa: unregulated dispersal of invasive species

Professional aquarists and hobbyists are thought to be the source of invasions of the aquarium strain of the green macroalga Caulerpa taxifolia in the Mediterranean, southern California, and Australia. The US Department of Agriculture, Animal and Plant Health Inspection Service (USDA–APHIS) restricted interstate commerce and importation of the Mediterranean clone of C taxifolia prior to the California invasion and is currently deciding if it should strengthen regulation of this genus as more species of Caulerpa are being described as invasive. Here we document the importance of e-commerce as a mode of dispersal for many species of Caulerpa in the United States. We purchased Caulerpa from 30 internet retailers and 60 internet auction sites representing 25 states and Great Britain. Twelve different Caulerpa species were confirmed using DNA sequencing. Only 10.6% of sellers provided the correct genus and species names with their shipments. Thirty purchases of “live rock” provided four species of Caulerpa, as...

RECREATIONAL BOATING ACTIVITY AND ITS IMPACT ON THE RECRUITMENT AND SURVIVAL OF THE OYSTER CRASSOSTREA VIRGINICA ON INTERTIDAL REEFS IN MOSQUITO LAGOON, FLORIDA

Abstract Along the east coast of central Florida in the Indian River Lagoon system, intense recreational boating activity occurs year-round, and intertidal reefs of the eastern oyster Crassostrea virginica (Gmelin) with dead margins (mounds of disarticulated shells) on their seaward edges are commonly found adjacent to major boating channels. These dead margins are caused, at least in part, by boat wakes and extend significantly higher above the high water line than reefs lacking dead margins (pristine reefs). To determine if these “impacted” oyster reefs alter recruitment and subsequent survival of C. virginica, three 8-wk field trials were run between May 2001 and April 2002 in Mosquito Lagoon. During each trial, data were also collected on total sediment loads, silt/clay fractions and relative water motion. Although recruitment did not differ between impacted and pristine reefs, juvenile survival was significantly reduced on impacted reefs. Additionally, larval recruitment and subsequent mortality were greatest during our summer trial. Total sediment loads, percent silt/clay, and relative water motion were significantly higher on impacted reefs. For these three variables, the largest values were consistently found at the bases of exposed (seaward) regions of impacted reefs. By documenting a positive relationship between reduced success of C. virginica and dead margins, and knowing that boat wakes contribute to the development of dead margins, we have provided the first cause and effect mechanism between intense recreational boating activity and increased oyster morality.

Exploring the Survival Threshold: A Study of Salinity Tolerance of the Nonnative Mussel Mytella charruana

ABSTRACT In this study, our objective was to understand life history attributes of Mytella charruana, a newly introduced species to the southeastern Atlantic coast of the United States, that would enable its survival in the introduced range. We therefore addressed the following questions regarding the range of salinities in which M. charruana can survive: First, in what range of salinities is survival possible for M. charruana if slowly adjusted to test salinities? Second, in what range of salinities can these mussels survive when experiencing rapid changes of salinity? Third, in what range of salinities can M. charruana survive with temporary, rapid changes of salinity (6-h duration)? We tested survival in salinities ranging from freshwater to hypersaline conditions (0–45 ppt) and determined whether mussel size affected experimental results. All experiments examined survivorship of mussels by increasing or decreasing the salinity from the field value under laboratory conditions. Mortality in each tank was recorded daily for 43 days for the gradual adjustment trials, and 12 days for permanent and 6-h shock trials. Large M. charruana (20–54 mm) survived best in salinities from 2–23 ppt, with 100% mortality at 0 ppt and 45 ppt with gradual adjustment. Small M. charruana (3–19 mm) survived in a wider range of salinities (2–40 ppt) with gradual adjustment to new salinities. However, survival of both large and small mussels was significantly lower in permanent shock trials at salinity extremes. Six-hour shock trials had no effect on survival at any of the test salinities (0–45 ppt) for both large and small M. charruana. Overall, the data indicate that these mussels could invade a wide variety of saline environments with significant freshwater or saltwater input.

Variability in the ecophysiology of Halimeda spp. (Chlorophyta, Bryopsidales) on Conch Reef, Florida Keys, USA

The photosynthetic performance, pigmentation, and growth of a Halimeda community were studied over a depth gradient on Conch Reef, Florida Keys, USA during summer–fall periods of 5 consecutive years. The physiology and growth of H. tuna (Ellis & Solander) Lamouroux and H. opuntia (L.) Lamouroux on this algal dominated reef were highly variable. Maximum rate of net photosynthesis (Pmax), respiration rate, and quantum efficiency (α) did not differ between populations of either species at 7 versus 21 m, even though the 21‐m site received a 66% lower photon flux density (PFD). Physiological parameters, as well as levels of photosynthetic pigments, varied temporally. Pmax, saturation irradiance, compensation irradiance, and growth were greatest in summer months, whereas α, chl a, chl b, and carotenoid concentrations were elevated each fall. Halimeda tuna growth rates were higher at 7 m compared with 21 m for only two of five growth trials. This may have arisen from variability in light and nutrient availability. Individuals growing at 7 m received a 29% greater PFD in August 2001 than in 1999. In August 1999 and 2001 seawater temperatures were uniform over the 14‐m gradient, whereas in August 2000 cold water regularly intruded upon the 21‐m but not the 7‐m site. These results illustrate the potentially dynamic relationship between nutrients, irradiance, and algal productivity. This suggests the necessity of long‐term monitoring over spatial and temporal gradients to accurately characterize factors that impact productivity.

Tracking the distribution of non-native marine invertebrates ( Mytella charruana, Perna viridis and Megabalanus coccopoma ) along the south-eastern USA

Our study tracked three non-native, marine, sessile, invertebrate species which have recently colonized the south-eastern United States Atlantic coastlines and estuaries: Mytella charruana, the charru mussel; Perna viridis, the Asian green mussel; and Megabalanus coccopoma, the titan acorn barnacle. Along the eastern Floridian coast, Mytella charruana was discovered in the Indian River Lagoon, Florida (FL) in 2004. Perna viridis was found in Ponce de Leon Inlet, FL in 2002, after being introduced to Tampa Bay, FL in 1989. Megabalanus coccopoma was documented in St Augustine, FL and Brunswick, Georgia in 2006. From 2006 through to 2011, a biannual survey of the south-eastern Atlantic coastlines and estuaries was conducted from Jupiter, Florida to Charleston, South Carolina (894 km) to document the distribution and range expansion of M. charruana, P. viridis and M. coccopoma. Field surveys were conducted in June and December each year at 82 sites (e.g. docks, boat ramps, jetties and mangrove roots). The ranges of the three invertebrates have expanded and retracted along the Atlantic coast since the survey began. Mytella charruana had spread as far north as Savannah, Georgia in 2007, but the species was absent from northern Georgia in 2010 and 2011. Perna viridis and M. coccopoma were present in Georgia in 2007, but were absent in the 2010 and 2011 surveys. These range fluctuations may be explained by extreme cold temperatures, which occurred during the 2009/2010 and 2010/2011 winters. The patterns observed with these three sessile invertebrates provide information regarding how non-native species disperse and establish in new locations.

FORMATION, MOVEMENT, AND RESTORATION OF DEAD INTERTIDAL OYSTER REEFS IN CANAVERAL NATIONAL SEASHORE AND MOSQUITO LAGOON, FLORIDA

ABSTRACT Globally, 85% of shellfish reefs have been lost during the past century. The severe loss of the eastern oyster Crassostrea virginica has encouraged different types of restoration efforts in the United States. In Mosquito Lagoon (ML), a shallow-water estuary on the east coast of central Florida, restoration focuses on providing additional substrate for larval recruitment via deployment of stabilized oyster shell. To assess the current number and area of natural, dead, and restored oyster reefs within ML, aerial photographs from 2009 were digitized using ArcGIS software. All reefs were screen digitized using a reef “signature” to estimate the surface area of each reef type. The maps from 2009 were then used as a guide to digitizing the historical aerial photographs (1943, 1951, 1967, 1971, 1984, 1995, and 2006). Oyster habitat within ML has decreased by almost 15 hectares between 1943 and 2009, which constitutes 24%of the 1943 lagoon-wide coverage. The impacts were greater in Canaveral National Seashore,which covers the southernML; 40%of the oyster coverage within the park has been lost since 1943. Dead reefs were found adjacent to important boating channels. Tracked dead reefs exhibited a continuous migration into the mangrove islands located landward of the original live reefs, with some dead reefs completely washing up into the marsh. Restoration of dead reefs with stabilized oyster shells has added nearly 1 hectare of live oyster habitat toML as of January 2009. This research demonstrates that dead reefs are increasing in number and coverage within ML, but this trend can be reversed with restoration.