Effects of urbanization on the nutritional ecology of a highly active coastal shark: Preliminary insights from trophic markers and body condition

• Published in: The Science of the total environment Vol. 826; p. 154082
• Main Authors: Rangel, Bianca S., Hammerschlag, Neil, Martinelli, Luiz A., Moreira, Renata Guimarães
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.06.2022
• Subjects: Animals; Body condition; Ecology; Fatty acids; Florida; Isotopes; Market gravity; Miami-Dade; Seafood; Sharks; Stable isotopes; Urbanization; Miami-Dade; Florida; Market gravity; Fatty acids; Stable isotopes; Body condition
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.154082

The synergistic effects of coastal urbanization have dramatically impacted biological communities. Yet, few studies have investigated how urbanization can influence the diet quality and trophic ecology of coastal sharks. In a preliminary study, we examined for spatial variation in the nutritional ecology of a highly active marine predator, the blacktip (Carcharhinus limbatus) exposed to regional differences in coastal urbanization in southeast Florida. We used medium-term nutritional indicators (i.e., body condition and whole blood stable isotopes [δ15N and δ13C]) and short-term dietary markers (i.e., plasma fatty acid profiles) to test the hypothesis that blacktip sharks sampled within highly urbanized areas (hereafter, ‘urban sharks’) would exhibit higher body condition, but lower diet quality, compared to conspecifics sampled in areas exposed to relatively low levels of urbanization (hereafter, ‘urban sharks’). Our initial results showed that urban blacktip sharks exhibited relatively higher body condition, blood δ15N levels, and percentages of saturated fatty acids compared to non-urban sharks. Collectively, these results suggest a possible positive alteration in the amount of food consumed by blacktip sharks in the study region and/or in the caloric value of their prey. We also found lower percentages of bacterial markers and higher values of dinoflagellate markers in urban sharks. Accordingly, we did not detect an expected reduction in diet quality (in terms of essential fatty acids) in this highly active species exposed to urbanization, as has been previously reported in a resident shark species (Ginglymostoma cirratum). Therefore, it is possible that lifestyle and feeding behavior influence the quality of food consumed by urban sharks. We suspect that impacts of urbanization are more pronounced in resident, sedentary and benthic species. [Display omitted] •Dietary patterns differed in blacktip sharks sampled in low and high-altered areas.•Body condition was higher in sharks exposed to high urbanization.•Urban sharks had higher percentages of saturated fatty acids and δ15N levels.•Sharks exposed to low urbanization had higher percentages of bacterial fatty acids.•Preliminary results suggest urban sharks consume more food resources.