VIETNAM NATIONAL UNIVERSITY, HANOI VNU UNIVERSITY OF SCIENCES FACULTY OF BIOLOGY Vu Ngoc Anh EFFECTS OF MARINE HEATWAVES AND FISH PREDATOR CUES ON THE GROWTH AND DEVELOPMENT OF Pseudodiaptomus incisus (Shen & Lee, 1963) UNDER LABORATORY CONDITIONS Submitted in partial fulfillment of the requirements for the degree of Master of Science in Biology Hanoi – 08/2024 VIETNAM NATIONAL UNIVERSITY, HANOI VNU UNIVERSITY OF SCIENCES FACULTY OF BIOLOGY Vu Ngoc Anh EFFECTS OF MARINE HEATWAVES AND FISH PREDATOR CUES ON THE GROWTH AND DEVELOPMENT OF Pseudodiaptomus incisus (Shen & Lee, 1963) UNDER LABORATORY CONDITIONS Major: Biology Major code: 8420101 Supervisor: Assoc. Truong Ngoc Kiem Hanoi, 8/2024 ACKNOWLEDGMENT First of all, I would like to express my sincere gratitude to my supervisors, Assoc. Truong Ngoc Kiem and Dr. Dinh Van Khuong, for their warm welcome, great motivation and inspiration, and invaluable advices.
Being their student, I have got the opportunity to learn how to conduct international-standard experiments, write scientific journals, be a leader, and become a professional scientist. My master’s thesis would never be accomplished without their help. Secondly, I would like to acknowledge Dr. Doan Xuan Nam and all the staff in Aquaculture Research Lab, Nha Trang University for supporting me during the experiment in Nha Trang.
I am also grateful to the lecturers, staff, seniors, and my counterparts, especially my dear friend, master student Nguyen Van Phuc, at the Faculty of Biology, VNU Hanoi University of Sciences, for giving me so many valuable comments, suggestions, and support both in my research and in life in general. Finally, I would like to send my thankfulness to my beloved parents, my ultimate role models, and all my family members for perennially supporting and encouraging me no matter what I pursue. They have always been standing by my side even when I was exhausted and frustrated because the experiment went wrong. This research was financially supported by the International Foundation for Science, Stockholm, Sweden, through a grant to Nam X.
In spite of making an effort to the thesis, due to the limitation of capacity, there are still inevitable mistakes in my thesis. I would greatly appreciate all comments to improve the quality of my thesis. With all of my sincerity and respect. Hanoi, June 14th,2024 Student Vu Ngoc Anh LIST OF ABBREVIATION MHW Marine heatwave FPC Fish predator cues TGP Transgenerational plasticity CT Control temperature i LIST OF FIGURES Figure 1.
Marine heatwaves (MHW) situation. (a) Annually time series of the number of the day that had MHW at any level (yellow), MHW at strong or higher level (orange), and the maximum intensity (blue); (b-d) MHW category (b), duration (c), and maximum difference of sea surface temperature (d) of extreme MHW………………………………………………………………………………. Prominent MHW events from 1982 to 2016. The numbers indicate the year when MHW occurred [28]…………………………………………………….
Sea surface temperature linear max temperature minus average temperature in Southeast Asian Sea [62]……………………………………………6 Figure 4. incisus a) nauplii; b) copepodite; c-d) mature female without (panel c) and with (panel d) egg sacs; e) mature male [Vu Ngoc Anh, 2020]………………. The schematic overview of the transgenerational experiment for the direct and transgenerational MHW and FPC effects on Pseudodiaptomus incisus (*CT: control temperature)………………………………………………………………. Sample collecting site map [Source: Google maps]…………………….
Stereo-microscope SZ51, by Olympus, Japan…………………………. The schematic of experimental design testing the direct and fccccccc transgenerational MHW and FPC effects on Pseudodiaptomus incisus…………. Effects of the marine heatwave (MHW) and fish predator cues (FPC) on the survival of males (a) and females (b) in F1 Pseudodiaptomus incisus. Data are visualized as mean ± SEs………………………………………………………….
Effects of the marine heatwave (MHW) and fish predator cues (FPC) on the number of eggs per clutch (a), percentage of females produced hatched eggs (b), hatched nauplii hatched from a clutch (c) of F1 Pseudodiaptomus incisus. Data are visualized as mean ± SEs…………………………………………………………. Effects of the marine heatwave (MHW) and fish predator cues (FPC) on cumulative nauplii per female (a) and faecal pellets per individual (b) of F1 Pseudodiaptomus incisus. Data are visualized as mean ± SEs…………………….
Immediate and transgenerational effects of the marine heatwave (MHW) and fish predator cues (FPC) on the survival rate (mean ± SE) of F2 Pseudodiaptomus incisus males (a) and females (b). *CT: control temperature…. The number of eggs per clutch (a), % females produced hatched eggs (b), hatched nauplii egg clutch (c) of F2 Pseudodiaptomus incisus. Data are visualized as mean ± SEs.
*CT: control temperature……………………………. Cumulative nauplii per female (a) and faecal pellets per individual (b) of F2 Pseudodiaptomus incisus. Data are visualized as mean ± SEs. *CT: control temperature…………………………………………………………………………35 Figure 15.
Effects of the marine heatwave (MHW) and fish predator cues (FPC) on the size at maturity of males (a) and females (b) of F1 Pseudodiaptomus incisus. Data are visualized as mean ± SEs…………………………………………………37 iii LIST OF TABLES Table 1. The results of the statistical analyses testing effects of marine heatwave (MHW) and fish predator cues (FPC) on survival, reproductive parameters and cumulative faecal pellets of F1 Pseudodiaptomus incisus. Significant P values are signed with *.
The results of statistical analyses testing the immediate and transgenerational effects of marine heatwave (MHW) and fish predator cues (FPC) on surival, reproductive parameters and cumulative faecal pellets of F2 Pseudodiaptomus incisus. Significant P values are signed with *. Summarising effects of MHW, FPC, and their interaction on Pseudodiaptomus incisus in two generations.36 iv TABLE OF CONTENTS INTRODUCTION………………………………………………………………… 1 Chapter 1 LITERATURE REVIEW……………………………………………. Definitions and drivers causing marine heatwaves………………….
History and prediction of marine heatwaves………………………… 3 1. Worldwide MHW situation……………………………………… 3 1. Southeast Asian Sea MHW situation……………………………. Ecological impacts of marine heatwave on marine organisms……… 6 1.
Fish predator cues………………………………………………………… 7 1. The role of predator cues to marine species…………………………. Transgenerational plasticity and parental effects…………………………. Definition and mechanisms………………………………………….
Roles of TGP under global climate changes………………………… 9 1. Multi-stressors effects on organisms……………………………………… 10 1. The importance of studying the effect of the combined many stressors10 1. Previous studies on the effect of marine heatwave and predator cues on marine species………………………………………………………………….
Biological characteristics of copepods……………………………………. The function of copepod………………………………………………11 1. The copepod Pseudodiaptomus incisus………………………………122 Chapter 2. OBJECTIVES, HYPOTHESES AND METHODS………………….
Objectives of the study……………………………………………………… 14 2. Implementation time and study site………………………………………. Materials and instruments………………………………………………… 16 2. Experimental design and set up……………………………………… 18 v 2.
Data analyses………………………………………………………… 20 Chapter 3. RESULTS AND DISCUSSION……………………………………. Effects of MHW, FPC, and their interactions on F1 generation of P. Effects of MHW, FPC, and their interactions on F2 generation of P.
Pleminary investigative results: Effects of MHW, FPC, and their interactions on the size at maturity of P. The direct effects of MHW, FPC, and their interaction (H1, H2, H3). Parental effects of MHW and FPC on F2 generation (H4, H5)……… 39 3. Transgenerational plasticity of P.
incisus to MHW, FPC, and their combination (H6, H7, H8)……………………………………………………. 43 APPENDIX 1……………………………………………………………………… 53 APPENDIX 2……………………………………………………………………… 59 APPENDIX 3……………………………………………………………………… 60 vi INTRODUCTION Climate change, especially marine heat waves (MHW), is one of the greatest threats to global biodiversity because extreme warm sea surface temperature during MHW are often beyond the optimal thermal range and last longer than one generation of tropical coastal species. Moreover, the pace of changing environmental conditions is much faster than the ability of organisms to develop adaptive responses. However, we know little about the role of MHW transgenerational acclimation in shaping coastal species, particularly an ecologically relevant context with biotic interactions such as predation stress.
Recent advancements in eco-evolutionary studies have revealed the critical important role of transgenerational plasticity (TGP), where the environment experienced by the parental generation may improve offspring performance in the same environment. TGP generally occurs through epigenetic changes, habitat selection, or niche construction. TGP is especially crucial for organisms to cope with new, predictable but fast changing and short-term environmental changes across generations, which is relevant to the duration of an MHW that often lasts longer than one generation for nearly all tropical zooplankton species. In the shallow tropical coastal ecosystems such as mangroves, seagrasses, and coral reefs, the predation stress is typically high as these ecosystems are the spawning and nursery ground of marine species.
Non-consumptive predation stress from voracious fish larvae and juveniles can significantly influence morphology, behavior, physiology, growth, and reproduction of the prey. Parental exposure to predators may also induce an increase in the reproduction of offspring generation and this effect may last two generations after exposure to predators. However, the TGP of prey species to predation stress may reduce in the degree of plasticity with an increasing number of exposed generations exposed to predators. Investigations of the transgenerational effect of MHWs in an ecologically relevant context, such as the presence of fish predator cues (FPC) on key zooplankton species, are relevant and timely with the increasing frequency, severity, and duration of MHWs and the intense predation stress of tropical coastal 1 environments.
Understanding whether copepods are resilient or vulnerable to MHWs in the context of predation stress is important, given that they are a key pathway for the transfer of energy and resources from photosynthesizing organisms to higher trophic levels, and ultimately the productivity of the coastal ecosystems. However, the combined effect of heatwaves and non-consumptive predation risk on prey species across generations is still a major knowledge gap in current ecological research. Our previous study shows that FPC induced a higher individual performance of the calanoid copepod Pseudodiaptomus incisus under control temperature, but it magnified the deleterious impacts of MHW on grazing and reproductive success. In this study, we address the knowledge gap identified above by assessing the immediate effect during the exposure together with the effects of parental exposure, TGP to MHW, FPC, and their interactions in a full orthogonal manner with 4 treatments in F1 and 16 treatments in F2 generation.
Definitions and drivers causing marine heatwaves Among several definitions proposed, marine heatwaves (MHW) are widely described as discrete periods of unusually high temperatures in a certain area which prolong for more than 5 days, as compared to the 90th percentile of average 30-year sea surface temperatures [41, 59, 73]. Besides, MHW were also defined based on higher percentiles to identify more extreme events; fixed limits relating to known species thresholds; or accumulated heat stress. The development and prolongation of MHW can be related profoundly to the atmospheric state such as high air–sea heat fluxes. In addition to this, the possibility of MHW occurrences regionally could be affected increased or decreased by the phase of climate modes of variability [59].
History and prediction of marine heatwaves 1. Worldwide MHW situation The term MHW was first referred to in 2011, when an unprecedented warming event occurred in the West coast of Australia, leading to a massive loss of kelp forest and changes in the associated ecosystems [73]. Since then, MHWs have become more common than ever before, increasing in frequency, duration, intensity, and distribution [28, 58]. In tropical areas, reports have indicated the appearance of nearly one to three MHW events per year on average, with the duration of 5-10 days [59].
Notably, in the Eastern Pacific, El Niño-Southern Oscillation events are considered as long-lasting MHWs, which lasted up to 60 days on average. In the extratropic regions except the Northeast and Southeast Pacific Ocean having MHW duration of up to 30 days, they are more regularly oscillating between 10 -15 days. Marine heatwaves (MHW) situation. (a) Annually time series of the number of the day that had MHW at any level (yellow), MHW at strong or higher level (orange), and the maximum intensity (blue); (b-d) MHW category (b), duration (c), and maximum difference of sea surface temperature (d) of extreme MHW [73] In addition to temporal scale, marine heatwaves have also expanded spatially.
The Mediterranean Sea heatwave event in 2003 was one of the first documented effects of MHW on the mortality of benthic communities [32].