Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Data Files
• Supplemental Files
• Related Publications
• Parameters
• Instruments
• Project Information
• Funding

These data were published in Nair et al. (2023).

Mnemiopsis leidyi and juvenile Callinectes similis were collected in March – April 2022, and Beroe ovata was collected in November 2022, using a plankton net (50 cm diameter, 500 μm mesh) from Aransas Pass inlet at Port Aransas (27.8396° N, 97.0726° W). Palaemon pugio was collected using a plankton net from Corpus Christi Bay (27.8035° N, 97.0898° W) in Port Aransas in July 2021. Opisthonema oglinum and Lagodon rhomboides were collected using a seine (6.4 m wide by 1.2 m high with 5 mm square mesh) from Aransas Pass inlet at Port Aransas (27.8396° N, 97.0726° W) in August 2021 and Redfish Bay at Aransas Pass (27.8611° N, 97.07632° W) in May 2022, respectively.

The live animals of each species were divided into two treatments (control and experimental). Both treatments were fed a common diet of either live Artemia sp. nauplii (enriched with Alga-Mac 3050; Aquafauna Bio-Marine, Inc.) or commercial fish food, Otohime (EP1, Reed Mariculture, Inc.) during the acclimation period of 10 – 45 days. After acclimation (Day 0), both treatments received a common diet of Artemia or Otohime, and the diet of experimental treatments was supplemented with red drum eggs for a period of 10 – 94 days. Controls did not receive eggs. Three to eight tanks of study species were sampled at the end of acclimation (day 0). Three to eight replicate tanks (N) were sampled from each treatment 24 h and 2 – 10 days after the experimental treatment received eggs.

Mnemiopsis leidyi, B. ovata, and C. similis were held in rectangular tanks (26.7 cm long x 16.5 cm high x 16.5 cm wide), and P. pugio and fishes were held in circular tanks (12 cm in diameter, 6.4 cm deep) with recirculating filtered water. Within each rectangular tank, individuals of C. similis were held separately in round plastic containers (106.7 cm in diameter, 43.2 cm deep) with perforated lids to prevent aggressive contact. For the same reason, individuals of L. rhomboides were kept in separate perforated cylindrical enclosures (30 cm in diameter, 45 cm high) within each circular tank. Excess food and solid waste were siphoned daily from all tanks, and complete water changes were performed in rectangular tanks every 2 – 4 days. Environmental conditions were measured daily and were constant throughout the experiment (temperature: 21 – 24°C, salinity: 28 – 35 ppt, and photoperiod: 12-h light and 12-h dark).

Invertebrates removed from both treatments on sampling days were kept in clean sea water overnight to evacuate their guts and were sacrificed the following morning. For taxa with low dry weight, i.e., ctenophores, 3 – 4 individuals from each tank were pooled together to make a replicate. A single individual per tank of C. similis, and three individuals of P. pugio (subsamples, n=3) per tank were removed at each sampling day. Invertebrates were analyzed whole, except for C. similis, for which the exoskeleton was excluded. On each sampling day, one fish per tank was removed and immediately euthanized with tricaine methanesulfonate (MS-222). Euthanized fish were placed on ice where a fillet of dorsal white muscle tissue were collected. Subsamples (n = 5 – 21) of diets provided to both treatments (i.e., red drum eggs, Artemia, and Otohime) were collected throughout the experiments for each taxon. All samples were rinsed twice in distilled water and frozen at -80°C until analysis.

A known subsample (0.5 – 0.7 mg of crustacean and fishes, 4.9 – 5.2 mg of M. leidyi, 1.0 – 1.2 mg of B. ovata) of lyophilized and homogenized tissue was weighed into a tin capsule at the UTMSI Core Isotope Facility. A Thermo Fisher Scientific Flash Elemental Analyzer-Isolink coupled to a Thermo Fisher Scientific Delta V Plus Isotope Ratio Mass Spectrometry (Thermo Fisher Scientific, Waltham, MA USA) in continuous-flow (Helium) mode was used to determine carbon and nitrogen isotopic compositions. Isotope analysis produced δ13C and δ15N values in permil or parts per thousand as well as percent carbon and percent nitrogen in the sample.

Experiments took place at the Fisheries and Mariculture Laboratory of the University of Texas Marine Science Institute (lat. 27.8396111, lon. -97.0827222) ; University of Texas Marine Science Institute Core Isotope facility (lat. 27.83669, lon. -97.05250)

ISODAT software (version 3.0) was used to collect the isotope trace chromatography and calculate raw isotopic ratios. Isotope results are presented using the conventional δ-notation:

δ¹³C (or δ¹⁵N)  = [(R_sample/R_standard)-1] (in ‰)

where, R_sample and R_standard = ¹³C/¹²C (or ¹⁵N/¹⁴N). All δ-values are reported relative to VPDB for carbon and AIR for nitrogen, unless otherwise stated (Coplen, 1996). A two-point calibration of δ¹³C to VPDB and to δ15N to AIR was achieved using USGS-40 (−26.39‰, −4.52‰) and USGS-41a (+36.55‰, +47.55‰), respectively. Internal laboratory standards; casein (protein), was used to evaluate the carbon and nitrogen accuracy and precision during analytical sessions. Overall, carbon and nitrogen isotope results had a standard deviation of less than 0.2‰.

BCO-DMO Data Manager Processing Notes:
* Sheet 1 of file "Stable isotope experimentals.xlsx" (submitted in our online submission system 2023-06-23) was imported into the BCO-DMO data system with values "NA" as missing data values. 
** Missing data values are displayed differently based on the file format you download.  They are blank in csv files, "NaN" in MatLab files, etc.
* Column names adjusted to conform to BCO-DMO naming conventions designed to support broad re-use by a variety of research tools and scripting languages. [Only numbers, letters, and underscores.  Can not start with a number]
* Taxon name and associated LSID for names in this dataset as of 2023-06-23 (source: World Register of Marine Species). Added this list to Methods and Sampling section.

NSF Award Abstract:
Marine animals release extremely large numbers of eggs when they spawn. Most of these eggs are eaten by animals ranging from microscopic plankton to fish. Many egg consumers are smaller than the animals that released the eggs, representing a reversal of the usual food web. The consumption of eggs provides animals with highly nutritious molecules called essential fatty acids which are very concentrated in eggs. These essential fatty acids are important for the health of animals and the health of the whole ecosystem. When marine fishes form spawning aggregations to coordinate the timing and location of spawning, they release trillions of eggs. This results in an "egg boon" an immense but temporary concentration of highly nutritious fatty acids. This project combines field-based sampling with laboratory experiments to assess how fatty acids in the egg boons affect food webs. The project is determining whether consumption of eggs is beneficial to the condition of the egg consumers. New findings from this project are advancing the understanding of aquatic food webs and contributing to improved management of marine resources. For example, commercial harvest of fish can remove tons of fatty acids from an ecosystem by reducing egg boons and leading to cascading and unforeseen effects on those biological communities. The project is fostering the participation of women in science by substantially advancing the professional training of a female postdoctoral fellow. The project is supporting K-12 STEM education through inquiry-based and place-based programs for teachers and youth. Findings are being communicated to the public locally and nationally through participation in public lectures and contributions to the Science and the SeaTM radio program, podcast, and website.

Super-abundances of eggs released in temporally and spatially discrete patches create pulsed nutritional resources for egg consumers, called "egg boons", which are potentially important components of marine food webs. While various marine animals have been shown to consume eggs, the role of egg boons in energy transfer through food webs has received little attention. Three hypotheses are being tested: 1) egg boons provide a pathway through which essential fatty acids (EFAs) are redistributed counter to the main direction of trophic flow; 2) stores of EFAs in egg consumers increase during egg boons and remain elevated after the spawning season; and 3) egg boons are beneficial to the condition of egg consumers. The proposed research takes advantage of an annual egg boon produced by a spawning aggregation of the marine fish, red drum (Sciaenops ocellatus) near Port Aransas, Texas. In a combination of field sampling and laboratory experiments, fatty acid profiles, lipid content, and bulk stable isotope ratios are measures used to define trophic links between the egg boon and a selection of lower-trophic-level taxa. Egg boons are simulated in laboratory feeding experiments that are designed to enhance interpretation of data collected from field based sampling by comparing taxa that consume fish eggs with those that do not. A nucleic acid biomarker (RNA/DNA ratios) is being used to assess changes in condition that can be attributed to egg consumption in target taxa. In the environment, the importance and persistence of counter-gradient flow of fatty acids in the food web is being gauged through comparisons of samples taken inside and outside the spatial and temporal extent of the egg boon. The effects of egg consumption on consumers is being quantified in controlled experiments to identify dietary biomarkers of egg consumption in consumer tissues that can be applied to field samples. The proposed research examines how egg consumption redistributes EFAs within food webs and provides a context for considering potential controls and trophic bottlenecks that cannot be explained from the traditional element-limitation models. The integration of fatty acid and stable isotope approaches is expected to provide greater resolution for tracking organic matter through food webs and to advance the application of multi-tracer techniques in trophic investigations. Further, if egg boons are indeed an important nutritional subsidy to select groups of consumers, then subsequent studies investigating the energetic contribution of egg boons to secondary production in marine food webs are warranted. An analysis of how reduction or removal of egg resources through the harvest of fishes in spawning aggregations changes nutrient flow in food webs could have implications for ecosystem-based fisheries management.