Extreme temperature impairs growth and productivity in a common tropical marine copepod

Abstract

Shallow, tropical marine ecosystems provide essential ecosystem goods and services, but it is unknown how these ecosystems will respond to the increased exposure to the temperature extremes that are likely to become more common as climate change progresses. To address this issue, we tracked the fitness and productivity of a key zooplankton species, the copepod Pseudodiaptomus annandalei, acclimated at two temperatures (30 and 34 °C) over three generations. 30 °C is the mean temperature in the shallow water of the coastal regions in Southeast Asia, while 34 °C simulated a temperature extreme that occurs frequently during the summer period. For each generation, we measured the size at maturity and reproductive success of individuals. In all three generations, we found strong negative effects of warming on all measured fitness-related parameters, including prolonged development time, reduced size at maturity, smaller clutch sizes, lower hatching success, and reduced naupliar production. Our results suggest that P. annandalei are already exposed to temperatures that exceed their upper thermal optimum. Increased exposure to extreme temperatures may reduce the abundance of these tropical marine copepods, and thus reduce the availability of resources to higher trophic levels.

Development of metal adaptation in a tropical marine zooplankton

“…While the impacts of widespread contaminants, such as metals [4][5][6] , on coastal species of this region are relatively unknown and poorly studied, newly emerging pollutants, such as plastics, arise rapidly 2,66 . The South China Sea is identified to be particularly vulnerable to climate change 15 , and climate change may further interact with contaminants to exacerbate the combined impact 17,67 . Altogether, it challenges efforts of biodiversity protection and management in one of the most biologically diverse and productive ecosystems on Earth, where substantial biodiversity loss has been documented 6,68,69 .…”

“…They are important grazers on small plankton 71 and prey for fish larvae and juveniles 26 . The development time of P. annandalei lasts from 9 to 11 days at a temperature range of 25-34 °C 15,72 . On average, a female produces 0.8 clutches per day (9 clutches or 18 egg sacs in 11 days 72 .…”

“…To start the experiment, 200 females (F0) carrying two egg sacs were collected from the culture, they were placed in a 5-L glass bottle at room temperature of 27 °C and fed ad libitum with T. pseudonana. All nauplii were collected after 30h 15 and ca. 150 nauplii were randomly assigned to each of 10 1-L bottles (five control and five Cu bottles) to start the F1 generation.…”

“…In general, organisms typically develop increased tolerance to long-term exposures to contaminants as a result of transgenerational plasticity, genetic adaptation, or both [8][9][10][11] . Multiple generational experiments have been applied to test how aquatic animals develop tolerance to stressors, such as metals 11 , polycyclic aromatic hydrocarbons 10 , pesticides 12 , algal toxins 13 , and temperature 14,15 . However, it remains a major challenge to detangle whether phenotypic changes in response to stressors are caused by transgenerational plasticity or from genetic adaptation.…”

Heat tolerance and thermal preference of the copepod Tigriopus californicus are insensitive to ecologically relevant dissolved oxygen levels

“…Marine organisms are facing increasing prevalence of multiple stressors, particularly extreme temperatures and heatwaves 1 – 5 and low dissolved oxygen 6 – 9 . Furthermore, stressors can interact and modulate each other’s effects 10 – 12 .…”