Donald Baltz

Louisiana State University | LSU · Department of Oceanography and Coastal Sciences (DOCS)

In 2013–2014, remote video and diver surveys documented fish assemblages around 150 small oil platforms in nearshore federal waters off the entire Louisiana coast (≤ 18 m depth). Results were used to evaluate ecological processes driving differences in fish abundance and assemblages associated with platforms. The nearshore zone was characterized by...

River-influenced ocean margins are dynamic and productive coastal environments. Nearshore Louisiana exemplifies the strong influence of the Mississippi and Atchafalaya rivers. Coastal salinities, temperatures, turbidities, and nutrients are directly affected, and the zone annually experiences the second largest eutrophication-induced marine hypoxic...

Oil and gas platforms (platforms) may provide important habitat for reef-associated organisms in the Gulf of Mexico's hypoxic zone. While summer hypoxia typically affects the bottom 3.0 m of the water column, platforms span from the bottom to above the surface and provide hard substrate in oxygenated waters overlaying hypoxia. However, little is kn...

There are >2,000 oil and gas platforms (platforms) in the northern Gulf of Mexico that are de facto artificial reefs. The ecological importance of platforms is the subject of debate, but little information exists on the extent that fishes feed on platform‐dwelling benthic organisms. We used a camera array to characterize the frequency and duration...

Nearshore oil and gas platforms (platforms) off Louisiana's coast occupy some of the most productive waters in the United States. Platforms are de facto artificial reefs with diverse fouling and fish communities, but little is known about the spatial dynamics of secondary production at platforms. In 2015 and 2016, we used settlement plates to compa...

River discharge and seasonal, eutrophication-driven hypoxia within coastal waters of the northern Gulf of Mexico create a wide range of environmental conditions for fishes. Environmental conditions are most dynamic on the Louisiana shelf, a region in which oil and gas platforms (hereafter platforms) are abundant and serve as artificial reefs. Platf...

Oil and gas platforms (platforms) provide high-relief habitat in the northern Gulf of Mexico’s hypoxic zone that are important to associated fishes. Hypoxia develops near the bottom and reef-associated fishes utilize vertical structure in the well-oxygenated waters overlaying hypoxia. A video array was used to profile the water column and to estima...

Oil and gas platforms are common in the northern Gulf of Mexico. Platforms provide substrate for sessile organisms such as barnacles and oysters that enhance habitat for stone crabs Menippe spp. and other fouling-associated organisms. In recent years, Louisiana’s small nearshore platforms (<15 m) have been subjected to a high rate of removal, but l...

Red Snapper Lutjanus campechanus in the northern Gulf of Mexico are threatened by the combined influence of fishing pressures, the bycatch of juveniles in the shrimp trawl fishery, and the seasonal formation of hypoxic (≤2 mg/L O2) bottom water along the Louisiana–Texas continental shelf. Juveniles are especially at risk from hypoxia because they l...

Tidal marsh restoration is an important management issue in the San Francisco Estuary (estuary). Restoration of large areas of tidal marsh is ongoing or planned in the lower estuary (up to 6,000 ha, Callaway et al. 2011). Large areas are proposed for restoration in the upper estuary under the Endangered Species Act biological opinions (3,237 ha) an...

Louisiana's 2012 Master Plan for a sustainable coast was designed to minimize economic damage from storm surges and to maximize wetland habitat for fish and wildlife. Selecting projects for inclusion in the master plan depended partly on models that simulated the effects of management options on environmental factors that control habitat quality fo...

This chapter analyse the coastal fish ecology, developing knowledge that leads to the wise and sustaainable management of fishes through studies that advance our understanding of bioenergetics, habitat requirements, predator-prey interactions, community dynamics, recruitment potential, and fisheries will have far-reaching benefits for the región, n...

On 20 April 2010, the Deepwater Horizon explosion, which released a US government—estimated 4.9 million barrels of crude oil into the Gulf of Mexico, was responsible for the death of 11 oil workers and, possibly, for an environmental disaster unparalleled in US history. For 87 consecutive days, the Macondo well continuously released crude oil into...

As an easy and relevant assessment within communities and arguably the most important in relating a species to its environment are its trophic interactions. Food webs and food chains offer visualizations of organismal connections, usually in direct predator–prey interactions. Nevertheless, indirect interactions and non-predator–prey interactions ar...

We compared nekton assemblages from natural and restored (or constructed) barrier island marsh habitats in two major estuaries in southeast Louisiana: Terrebonne/Timbalier Bay and Barataria Bay. We targeted barrier island marshes, because they are rapidly disappearing from natural (erosion and washover during storms) and anthropogenic causes (dredg...

Two morphologically dissimilar stream fishes occupied the same microhabitat in different riffles of Deer Creek, Tehama County, California. In a 12.5 km reach of the creek, speckled dace (Rhinichthys osculus) dominated riffles at the lower end while riffle sculpin (Cottus gulosus) dominated the riffles at the upper end, where dace were confined to s...

Harmful algal blooms are an increasing problem for coastal waters world-wide. The presence of the toxigenic diatom genus Pseudo-nitzschia is of concern in the Gulf of Mexico, due to the potential for several species in this genus to produce the neurotoxin domoic acid (DA). Louisiana coastal waters are of particular interest due to the presence of b...

A description of the foraging habitat of a cetacean species is critical for conservation and effective management. We used a fine-scale microhabitat approach to examine patterns in bottlenose dolphin (Tursiops truncatus) foraging distribution in relation to dissolved oxygen, turbidity, salinity, water depth, water temperature, and distance from sho...

Although eutrophication in the northern Gulf of Mexico contributes to the high fisheries productivity characteristic of the region, nutrient over-enrichment leads to the seasonal formation of hypoxic (≤ 2 mg L− 1 O2) bottom water along the Louisiana–Texas continental shelf. Despite an increase in the magnitude and duration of hypoxic episodes in re...

On 19 April 2005, an oil spill occurred in southeastern Louisiana’s Barataria Bay estuary. We used a drop sampler to characterize the marsh-edge nekton community. Thirty-six locations were sampled in pre- and post-spill time frames from March through May 2005. Before–after control–impact (BACI) analyses of the total number of individuals (fishes +...

We examined patterns of habitat use by fishes and decapod crustaceans in a seemingly pristine tidal stream system that drains into southeastern coastal Louisiana, northern Gulf of Mexico. The study area centered on a relatively unaltered mesohaline saltmarsh nested within more heavily degraded conditions. Monthly sampling (February–November 2004) s...

In response to a request by American Fisheries Society President Christopher Kohler, we examined the current status of open ocean aquaculture in the Exclusive Economic Zone (EEZ) of the United States, interest in open ocean aquaculture activities, the regulatory environment, and the potential for sustainable development. There is currently little i...

The northern Gulf of Mexico supports substantial commercial and recreational fisheries. While landings have remained strong throughout recent years, the seasonal formation of hypoxic bottom waters is a threat to long-term sustainability of regional fisheries production. Because nekton are mobile, the greatest threat to fisheries resources is likely...

Chemical additives for enhancing deepwater (>305-m) petrochemical production, such as ethylene glycol and methanol, are used to prevent the formation of gas hydrates in deepwater wells and pipelines and pose threats to marine faunas. Juvenile Florida pompano Trachinotus carolinus were used in controlled experiments to test the effects of 3.0% (volu...

Deepwater petroleum production requires that a number of additives, such as methanol, be transported offshore in large quantities, posing the risk of spills. Although these additives may not be highly toxic per se, it is important to evaluate and understand the risks to marine organisms, especially fishes that are often strongly associated with oil...

We examined patterns of resource utilisation between young-of-the-year blackcheek tonguefish ( Symphurus plagiusa) and offshore tonguefish ( S. civitatium), in Barataria Bay, Louisiana, USA. A stratified monthly sampling approach was implemented to facilitate sampling of the broad saline to brackish estuary along environmental gradients. At each si...

Daily otolith increment widths of spot Leiostomus xanthurus and spotted seatrout Cynoscion nebulosus were examined experimentally in field mesocosms for 5 to 7 days in various habitat types. Daily otolith increments were used as a surrogate for daily somatic growth so that growth prior to capture and handling could be examined. For both species, po...

We used a 1-m beam trawl to characterize microhabitat use by fishes and decapod crustaceans in monthly samples collected in Vermilion and West Cote Blanche bays in central coastal Louisiana. Randomized sampling within strata characterized the distributions of species, size-classes, and environmental conditions throughout the coastal bays. Microhabi...

Brown shrimp (Farfantepenaeus aztecus) are an important commercial aquatic species experiencing loss of inshore marsh nursery habitat in coastal Louisiana. To study inshore brown shrimp movements and identify aspects of essential habitat important for sustaining brown shrimp populations, we collected juvenile brown shrimp in April and May 2000, the...

Exposure to ethylene glycol, an additive in petroleum production, may not be immediately lethal to fishes but does affect swimming performance. All life history stages of Florida pompano Trachinotus carolinus are at risk of exposure from spills in the coastal and deep waters of the northern Gulf of Mexico. Toxicity tests on juvenile fish and subseq...

Exposure to ethylene glycol, an additive in petroleum production, may not be immediately lethal to fishes but does affect swimming performance. All life history stages of Florida pompano Trachinotus carolinus are at risk of exposure from spills in the coastal and deep waters of the northern Gulf of Mexico.Toxicity tests on juvenile fish and subsequ...

We examined patterns of resource use by size classes of fishes and macroinvertebrates in Barataria Bay, Louisiana. Analyses were based on microhabitat data characterized by water depth, distance from shore, substrate, salinity, dissolved oxygen and temperature. Stratified random samples along the salinity gradient from the nearshore Gulf of Mexico...

Kinesins are cytoskeletal motor proteins that play roles in a variety of fundamental cellular processes including cell division and the anterograde transport of vesicles and organelles. We purified, cloned, and functionally characterized in Trypanosoma brucei a new member of the C-terminal kinesin family, TbKIFC1. Kinetic constants of the recombina...

In trypanosomatids, removal of hydrogen peroxide and other aryl and alkyl peroxides is achieved by the NADPH-dependent trypanothione peroxidase system, whose components are trypanothione reductase (TRYR), trypanothione, tryparedoxin (TRYX) and tryparedoxin peroxidase (TRYP). Here, we report the cloning of a multi-copy tryparedoxin peroxidase gene (...

In Trypanosoma brucei, we have cloned a gene approximately 5 kb downstream of the glucose transporter gene cluster, containing a variable number of 102 bp repeats. This gene encodes a protein with no homologues in the data bases. Antibodies raised against the 34 amino acids repeated motif recognized proteins ranging from 145 to 270 kDa, depending o...

The northern Gulf of Mexico is an economically important coastal zone that produces large yields of fish and shellfish. Because of the documented impacts low oxygen can have on living resources, hypoxic bottom waters (< 2.0 mg 1−1) that form along the coast are viewed as a threat to sustained fisheries production in the region. We reviewed factors...

Two species of tonguefishes,Symphurus plagiusa (Linnaeus 1766) andSymphurus civitatium Ginsburg 1951, occur sympatrically and sometimes syntopically in shallow water habitats in North Carolina and Louisiana estuaries. In North Carolina, approximately 2% of 430 small (<75 mm SL) tonguefishes collected wereS. civitatium, while in Barataria Bay, Louis...

Stimulated by nutrients from the Mississippi River, the vast coastal wetlands of the river's past and present deltas interface with the Gulf of Mexico to form a complex and prolific marine ecosystem. This highly productive system has yielded annual fishery landings of >453.6 x 10(6) kg (1 billion pounds) since 1969. The Louisiana ecosystem has been...

Trypanosomatids are unicellular protozoan parasites which constitute some of the most primitive eukaryotes. Leishmania spp, Trypanosoma cruzi and members of the Trypanosoma brucei group, which cause human diseases, are the most studied representatives of this large family. Here we report a comparative analysis of a large genomic region containing g...

The relationships among microhabitat use, food habits, conspecific density and recent growth rate for estuarine-dependent juvenile spotted seatrout, Cynoscion nebulosus, and red drum, Sciaenops ocellatus, were studied to determine how nursery habitat influences early growth. Juvenile spotted seatrout and red drum were quantified along the marsh-edg...

Trypanosomatids are parasitic protists that have an ATP-dependent glycolysis with no indication of PPi-dependent metabolism. Most of the glycolysis takes place in peroxisome-like organelles, the glycosomes. We characterized in Trypanosoma brucei a single-copy gene encoding a PPi-dependent enzyme, pyruvate, phosphate dikinase (PPDK), which was expre...

Trypanosomatids are unicellular protozoan parasites which constitute some of the most primitive eukaryotes. Leishmania spp, Trypanosoma cruzi and members of the Trypanosoma brucei group, which cause human diseases, are the most studied representatives of this large family. Here we report a comparative analysis of a large genomic region containing g...

Since the exotic Eurasian milfoil Myriophyllum spicatum (L.) was first reported in the Lake Pontchartrain estuary in 1978, it has become established as a dominant species of submerged macrophyte, but its distribution and abundance have varied considerably. We compared fish assemblages among two native macrophytes, Vallisneriaamericana (Michx) and R...

We used a 1 m beam trawl to characterize microhabitat use of flatfishes in monthly samples collected in Barataria Bay, Louisiana. Six strata were established along a salinity gradient from the nearshore zone along the Gulf of Mexico to approximately 30 km inland. Randomized sampling within strata characterized flatfish distributions and environment...

Assemblages of native stream fishes in California show a remarkable ability to resist invasion by introduced fishes as long as the streams are relatively undisturbed by human activity. Previous studies had indicated a high degree of spatial (microhabitat) segregation among the native fishes, which was confirmed by a principal components analysis of...

Spawning site selection by spotted seatrout and black drum was studied by locating drumming aggregations through the use of a hydrophone. From March 1987 to October 1990, 315 sound observations were made to identify and characterize spawning seasons and environmental requirements of both species in the Barataria, Caminada, and eastern Timbalier Bay...

We used a drop sampler to characterize use of the marsh-edge ecotone by small fishes along two transects running inland from the Gulf of Mexico for ca. 25 km in Louisiana's Barataria-Caminada Bay System. Monthly sampling was stratified among upper, middle, and lower reaches and within reaches to characterize fish responses to salinity, depth, dista...

Patterns in the community structure of marsh-edge fishes occupying the ecotone between marsh surface and open water were revealed through intensive surveys with a drop sampler along two 25 km transects in a Louisiana estuary during spring and summer 1989. We quantified abundances of organisms and measured environmental variables to characterize com...

Shifts in microhabitat selection by rainbow trout Oncorhynchus mykiss were related to seasonal and ontogenetic factors in a small stream characterized by short riffles, small pools, and boulder substrate. Resource availability did not differ significantly between summer and November sampling dates for most variables related to water velocity, subst...

The number of introduced marine and estuarine fishes is small compared to that of freshwater introductions. Nevertheless, the number now exceeds 120 species and the list is growing. Many have been intentional introductions to enhance fisheries, but the majority are the unintentional result of canal construction and ballast-water transport. While ba...

During 21 months of sampling with various techniques, we captured 24 species of fish in Britton Reservoir. Nine species comprised over 96% of the number of fish captured and approximately 88% of the biomass. Five native non-game species accounted for over 77% of the catches.The native non-game fishes have maintained large populations in the reservo...

Diadenosine 5′,5″′-P1, P4-tetraphosphate (Ap4A) binding protein specifically binds Ap4A. The protein has been purified from Xenopus laevis oocytes and presents and estimated molecular weight of 100,000 by gek filtration. In the first stages of the purification, the Ap4A binding activity is found associated to DNA polymerase alpha-DNA primase, formi...

We used eight microhabitat variables to examine the assumption that the variables normally included in instream flow studies are adequate to discriminate among species' micro- habitats. When eight variables were available in stepwise-discriminant analysis models to distin- guish among the microhabitats of four fish species in a northern California...

African trypanosomes are thought to evade the host immune system by periodically changing their variable surface glycoprotein (VSG). VSG genes are activated by a complex process involving the duplicative transposition of silent basic copy genes to one of several expression sites. These expression-linked copies (ELCs) of the VSG genes are also subje...

The patterns of distribution and abundance of the fishes of Suisun Marsh, a portion of the Sacramento­ San Joaquin estuary in central California, were studied over a 54-month period. Thtal fish abundance in the marsh exhibited strong seasonality; numbers and biomass were lowest in winter and spring and highest in late summer. Freshwater inflow was...

Based on analysis of catch-per-unit-effort trapping data for a shallow, soft-bottomed estuarine system (Barataria Bay), depth appeared to be a more important habitat-selection factor than substate for a Louisiana population of stone crabs (Menippe adina). The primary substate type and its interaction with depth contributed significantly to the pred...

Microhabitat requirements were determined for eight species of native California stream fishes: Rainbow trout Salmo gairdneri; Sacramento sucker Catostomus occidentalis; Sacramento squawfish Ptychocheilus grandis; hardhead Mylopharodon conocephalus; California roach Hesperoleucus symmetricus; speckled dace Rhinichthys osculus; tule perch Hysterocar...

A semi-defined medium for the cultivation of bloodstream forms of the African trypanosome brucei subgroup was developed. Out of 14 different strains tested, 10 could be cultured including Trypanosoma brucei, T. equiperdum, T. evansi, T. rhodesiense and T. gambiense. The presence of a reducing agent (2-mercaptoethanol or thioglycerol) was found to b...

Life history variation within the family Embiotocidae is extensive and involves differences in age of first reproduction, fecundity schedules, growth rates, longevity and size of young. Based on maximum reported body lengths, there are three distinct size groups among the family''s 23 species. Small species do not exceed 215 mm TL, medium-size spec...

African trypanosomes evade clearance in immune-competent hosts by periodically replacing their major surface glycoprotein with an antigenically different glycoprotein. Expression of many of these variant surface glycoproteins (VSGs) is associated with the duplication and transposition of silent basic copy genes (BCs) into unlinked genomic expressio...

The hypothesis that Sacramento suckers, Catostomus occidentalis, compete with rainbow trout, Salmo gairdneri, for space in streams was examined by measuring microhabitat utilization of both species in three California streams. Two streams were similar in most respects except one contained only trout and one contained trout and a large population of...

1.1. Embryos of the viviparous embiotocid fishes develop free within the ovarian cavity from small eggs for approximately 6 months. The biochemical composition of ovarian fluid was determined and compared to serum constituents in three embiotocid species during the gestation phase.2.2. SDS-gel electrophoresis data showed that ovarian fluid collecte...

Monoclonal antibodies directed against RNA polymerase B of the fungus Podospora comata were selected on the basis of different subunits recognition and inhibitory effect on enzyme activity. A library of 10 antibodies biased toward B180, B145, B39, B23,5 and B11 subunits was constructed. Most of these antibodies also recognize yeast, wheat germ and...

The cross-reacting antigenic determinant in the variant surface glycoproteins (VSGs) of Trypanosoma equiperdum was studied by testing the ability of VSG glycopeptides to bind heterologous anti-VSG sera. VSG glycopeptide purification revealed the presence of 3 oligosaccharide sidechains on the mature VSG. These consist of two sidechains containing o...